Onward Air Transmission

Onward Air Transmission markings occurred between 1940 and 1973 with their greatest use being between 1943 and 1946 and peaking in 1945. Often they are associated with AV2 markings, but the latter topic is outside the scope of this article. Suffice it to say, AV2 markings were used principally as a summary of what a bag contained and how it was to be handled. An AV2 marking is shown as an illustration.

OAT can also stand for Onward Air Travel (probably English, while Transmission sounds American). It is thought that an OAT cachet was applied to the top letter of a tied bundle of up to 60 letters. These bundles always travelled in open mail bags to a single intermediate or final destination, but where the quantity of mail was insufficient to warrant a closed bag. Closed mail bags did not attract OAT markings, as the whole bag was sealed and all letters went to the one destination as marked on the outside of the bag. Open mail bags were resorted en route as required and bundles replaced into other bags for the next section of their journey.

The use of OAT markings was discretionary. Routes and methods of mail conveyance were always changing during the war, due to the military situation. The bulk of OAT markings were applied in the Foreign Section of the London Post Office during and after WW2. This meant that all this mail was being routed through London for censorship (many) and forwarding. Censorship also provided considerable intelligence for the Allied war effort.

Lisbon was the main staging post for the London mail run from Africa, USA or further east, especially during the colder months. Gibraltar was also used from later 1943, once the Mediterranean area was cleared of the German and Italian forces.

Until 1952, a letter could be paid part of the way by air and part by sea. After 1952 airmail rates applied for the whole journey only. Thus the purpose of the OAT marking was to denote onward air travel, even if the rate paid was for sea mail or partly paid airmail. During the war, mail handling was simplified as much as possible, so that it permitted it to get through at all. Optional part way by air often was an unwanted complication for the postal authorities.

While the UPU convention of 1929 covered handling of airmail letters, postcards, etc, the use of OAT markings was nowhere specified within their regulations – thus they were unauthorised. The increase of airmail letters & the exigencies of war often required novel approaches to mail handling. This was no exception.

Being used on the top letter of a bundle, in effect as “sleepers”, OAT markings are comparatively rare. Heifetz 1 lists some 6000 in his 2006 database as being known worldwide then of all types. He scoured auction catalogues and others’ holdings to get numbers and then analysed the source, destination and cachet type to compile his database. While this sounds easy, wartime OAT cachets certainly, having rubber faces, were prone to distortion when being applied. This made analysis of cachet type more difficult, since size of both the outside oval or rectangle and the O.A.T. contained therein were collected to assist classification.

Donald Smythe in 1962 was the first person to attempt some classification of OAT markings in an article published in the September 1962 edition of the American Philatelist. Others have added to it or even published their own systems. Kristian Hopballe has written two articles on Icelandic and Faroese OAT markings and used Smythe’s classification. The Smythe system is the most popular basis for listing them, and as such has become the de facto standard. Only markings on flown covers are included by Heifetz. On occasions, private markings have been noted (forgeries?), which were excluded.

Sizes noted by Heifetz are assumed to be ±2 mm, especially the outer oval or rectangle (due to distortion), while the letters are closer. Luckily, different combinations of OAT length, height and letter peculiarities come to our aid in classifying which type is being studied. What it is not is often helpful in reducing one’s choice. It is mostly easier than one might think to arrive at the correct type. Rubber cachets at this time did have not good solvent resistance and the ink’s solvents caused swelling, softening and degradation with the resultant distortion. As an aside, my investigations into cachet polymer type and ink solvents used have so far elicited no information. I have my theories!

Most OAT marks are in a pale pink or pink-red ink, which in itself may vary, due to fading, amount of ink used etc. Blue, violet and black inks are also known for some types of cachet. It is thought that there were ‘desks’ designated for censoring or gathering mail from a group of destinations, where the language in which the letters were mostly written was common. This made the censor’s work easier, even though many letters escaped censorship in London, this having been done elsewhere if required. Thus, certain types of cachet predominate for particular sources of letter and often destinations. Heifetz lists these under each cachet number (type).

While different coloured cachets are noted by type, Heifetz does not give any numerical comparison for their use, other than note a premium for other colours over pale red. Certainly, during the war, colours other than red are far harder to come by in practice.

Throughout the war, Lisbon was available to forward mail to the UK. As Portugal was neutral during WW2, Pan-Am as well as BOAC and German airlines used it. However, after America’s entry into the war, no mail from occupied Europe was forwarded by the Germans for transmission through Lisbon after April 1942. Vichy France could send and receive letters until the November 1942 invasion of French colonies in Africa and the Middle East by the Allies.

Most mail to the Americas went either via Pan-Am’s Caribbean or South American routes from there, although, after 1942 mail went via Ireland and Greenland during the summer months. Seaplanes were used, landing in the Tagus river for Lisbon for instance until 1944, when longer range land based planes became available. Routes traversed Africa south of the war zone to connect with countries further east (eg Horseshoe route). Again flying boats were used initially, so water was required for landings. Mail from South African countries was carried by SAA or Sabena in land planes to Lagos, where it changed to flying boats.

Depending where the Allies or enemy fronts were, so routes were either cut or became available, sometimes causing severe disruption to airmails. Thus mails, despite being marked OAT, could travel much of the way by sea, depending on their destination. Delays were also considerable, either waiting for planes or ships to be available. Mail did not always have the highest priorities, urgent war supplies or Staff movements could take precedence. The Horseshoe route to Australia was one such with, firstly the Mediterranean theatre and later the fall of Singapore, Indonesia and Burma. The study of routes during WW2 is well listed by Thomas Boyle Jnr in Air Mail Operations During World War II, A Study of Routes, Rates and Markings. Routes for items shown only will be discussed.

Heifetz devotes three pages to a summary of these and their effects on types of cachet and frequency of use in his second edition. His last paragraph is worth citing in part: “Out of 2400 covers, 1453 are to three countries – USA, Sweden and Switzerland. Sweden & Switzerland were neutral throughout the war and USA till December 1941, thus airmail services were more available (not really so! – most OAT marks were applied in UK – MB). Swiss covers are mostly related to the Red Cross. Swedish & USA are both related to procurement of materials for wartime manufacture.”

Heifetz lists twenty different types of OAT marking with a couple of sub-groups. One of these is for manuscript markings, of which 26 are recorded. Some of these types are rare, with very few covers seen. Others are the work horses of the system and hence relatively common. During the war period, all cachets had oval shaped surrounds or no surround at all. Smaller rectangular ones began to appear from 1945 onwards. Four OAT/FS cachets, (thought to be for Foreign Section) with oval or rectangular frames, appeared from 1948. These last were low usage as post-war commercial airline flights no longer needed to go via London, nor was censorship required then in the West.

Heifetz has classified OAT markings by occurrence, colour, country of origin and country of destination to establish some relative values. A is the rarest, while G is most common. Some 57 or around 1% of the 6000 markings had not been identified. The main problem would have been poor quality strikes, so that too small a portion was visible (cf cds marks on letters, where the details are indecipherable).

Frequency of occurrence of a particular OAT type. (type listings are always in Roman numerals)

A = 1 – XIIIa, XVa,
B = 2 – 5 – XIIIb, XVIIa, XIXa
D = 16 – 40 – XII, XIV, XV, XVIII and manuscript
E = 41 – 75 – X, XIII, XVII
F = 76 – 125 – II, IIIa, VIII
G = >125 – I, III, IV, V, VI, VII, IX, XI, XVI, XIX

OAT I is the commonest of all types and was the only OAT marking in use throughout the real (not phoney) war. Those shown in bold are illustrated in this article.

Country of Origin (only three grades listed for simplicity)

A = 47 Administrations D = USA, Egypt, Turkey, New Zealand, Faeroes etc G= South Africa, Belgium, Palestine, Tangier/Tetuan, India etc

Country of Destination (again only three grades listed for simplicity)

A = 36 Administrations D = UK, Belgium, New Zealand, Ceylon, Kenya, Germany etc G = USA, Sweden, Canada, Switzerland, India, Palestine

Ink colour

OAT I – Black, violet or blue have a premium over red
OAT III and IV – Black and violet have a premium over red
OAT XI and XII – Black has a premium over red
OAT XVI – Violet more common than black or red

Frequency of markings by year (only main years cited). Note the great increase in items recorded between 2nd and 3rd editions of Heifetz’ book.

Precursors to the OAT markings originated from the Far East with the Netherlands East Indies (NEI) and Hong Kong. Rather than being the top letter of a bundle, it is believed every NEI letter (and they are few) was marked. Certain airmail letters in Hong Kong, during censorship, often on transit mail to & from Shanghai were marked with numbered circular Air-Transit handstamps. Both are seen from 1940 until the Japanese invasion halted all movement of mails. Firstly, there are two NEI letters:

Double weight airmail letter from Batavia to Perth

By Q.E.A. to Australia and Onward Air Transmission. Batavia cds of 1 Oct 1941. Censored at Batavia with Dev. 9, showing financial censor’s number, but unopened.

Postage 15c (≤ 20 gm)
Airmail to Oz 20c (5c per 5 gm)
Airmail D to P 20c (5c per 5 gm)
Route was Batavia, Koepang, Darwin and Perth.

Nonuple (9x) weight airmail letter from Batavia to New York

KNILM Trans Tasman / PAA and Onward Air Transmission. US Government Supp Sed… Batavia (Centrum) cds of 23 November 1940. Censored at Batavia then stamped both sides on tape with red Dev. 8 cachet of financial censor

Postage 15c (≤ 20 gm)
Additional 20c (10c / 20 gm)
Airmail USA 5.85 G (65c / 5 gm)

Route was Batavia to Sydney by KNILM, then to Auckland by TEAL. From Auckland, it picked up Pan-Am FAM-19 Clipper flying boat service to San Pedro, via Noumea, Canton Island and Honolulu.

This was a bank to bank letter, to which the endorsement Supp Sed note below applied.

Air Mail Covers with Executive Order 8389 Handstamps
During the war, some incoming air mail letters from a few foreign countries bear a handstamp which reads “SUPPOSED TO CONTAIN MATTER / SUBJECT TO THE PROVISIONS OF / EXECUTIVE ORDER 8389 AS AMENDED”. Executive Order 8389 pertained to the regulation of certain financial transactions, transfers of credit, and export of coin and currency to countries occupied or controlled by Germany, and to Germany itself. The “as amended” phrase pertained to the fact that the basic order was amended during the progress of the war to include countries invaded by the Axis partners. The handstamp identified the mail as being suspected of having non-allowable financial material enclosed. The procedure required that the postal office notify the addressee to send the person named in the address, or, if no person was named, to send an authorized agent of the addressee, to the post office to open the mail in the presence of postal officials. Financial documents and material were examined and banned material was confiscated. The correspondence and the envelope were then passed to a censor (if deemed appropriate), and the mail was delivered to the addressee by regular postal delivery services. An example of an incoming letter with the handstamp applied that referred to Executive Order No. 8389 is shown in Figure 233 in Chapter 13.

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Air-Transit Marking

Registered airmail letter from Shanghai to Limoges (Vichy France)

Shanghai cds of 26 Sep 1941. Blue-black Registered hand stamp & in m/s. Registration label Shanghai S.O 13 No. 6336. Typed notation Pan American Air Lines / San Francisco – New York – Lisbonne. Light violet Air-Transit 2 cachet applied in Hong Kong

Boxed lt violet 126 initial censor’s No. Opened by censor closure label (verso). Black illegible censor cachet (over Shanghai cds – verso) tying closure. Violet boxed 27 censor’s number tied to closure (verso). Large blue S.R (verso)

Blue Honolulu registerd cds (verso). 5 Nov 1941? Black oval New York U.S.A / Foreign datestamp of 8 Nov 1941 (verso) Red Bermuda censorship number 45418 showing it passed there but was not censored (verso). Black Limoges / Hte Vienne arrival cds 5 Dec ? 1941 (verso)

Franking
Postage (≤ 20 gm) 50c
Registration 50c Airmail (per 5 gm) $5.40c

Routing of letter
1 Between Hong Kong and Shanghai, this letter went by boat.
2. From Hong Kong by PAA FAM-14 to San Francisco via Manila and Honolulu.
3. San Francisco to New York, most likely by train.
4. From New York to Lisbon by PAA FAM-18 main route as it acquired a Bermuda censor number there.
5. Then on to Lisbon via the Azores.
6. At Lisbon, which was neutral, the letter changed to the German controlled posts.
7. From Lisbon it went to Madrid. German DLH regularly flew to Madrid, Barcelona, Marseille and Lyon and on to Munich, so it may have gone to Lyon by air.
8. North by air to Limoges via Vichy on scheduled flight.

FAM-14, FAM-19 routes

FAM-18 routes RHS

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AV2 Markings. Use in an open bag to alert postal authorities that an AV2 form was enclosed.

Airmail letter from Lucknow to Philadelphia

Lucknow cds of 6 Mar 1941 (R). Victoria / Hong Kong transit cds of 24 Mar 41 (R). Censored in Delhi and closed with brown tape. Triangular passed by censor A14 of Delhi (R) in black. Violet rectangular not opened by censor (R) at Hong Kong. Pale violet AV2 (R). Postage ** 2 R 11½ A (inc airmail for ≤ ½ oz)

Note** From Boyle (p794) the rate paid applied from Jul – 15 Oct 40. From then until mid July 41 the new rate was 3 R 10½ A by the transit route below. With the closure of the Empire route due the Italian entry into the war, only the route via Hong Kong was then available for mail from India.

Transit route
Lucknow to Delhi by rail. BOAC to Rangoon (p788). CNAC to Hong Kong via Lashio, Kunming, Kweiyang & Kweilio (p755) (see map below). AV2 cachet added in Hong Kong. Hong Kong to Manila then FAM-14 to USA with Pan-Am. Finally by train to Philadelphia.

From October 1940 all mail to Hong Kong went by the above route via China, due presumably to Indo-China being Vichy Government controlled and thus safety could not be guaranteed overflying. Also Saigon could not be used as a refuelling stop anymore.

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Letters with various OAT cachets

Letter from Johannesburg to Stockholm with red OAT type I cachet applied in London

Johannesburg 106 cds of 18 March 1943. Censored at Johannesburg by Censor I 7 (verso) and closed using bilingual closure. A.P.O. – U – … transit cds of 20 Mar 43 applied in Johannesburg after censoring.

1/3d airmail rate applied to London, but as the only mail to London, but as the only mail to Sweden was by air from Prestwick or Leuchars to Stockholm as a night flight, seamail was not an option – hence the OAT mark.

From Jan 28 1942, SABENA and SAA flew alternate weeks from Cape Town to Leopoldville via Johannesburg, Bulawayo, Lusaka and Elisabethville and returned with southbound mail. (This was an important link for the Horseshoe route). From Leopoldville it went by BOAC to Lagos, Lisbon and Foynes (Eire). Then to London (OAT applied), train to Prestwick & BOAC or to Leuchars & ABA flight to Stockholm.

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Letter from Stockholm to Australia with red OAT type I cachet applied in London

Alsten CDS of 6 August 1942 (Stockholm suburb) Manuscript notation 20 Oct 42 (arrival) Manuscript (partly covered) Australien & Flygpost! via England Censored in Melbourne – 3/passed/by/censor/157 3 opened by censor in red on closure

Postage
30 øre s 20 gms and airmail Sweden-Australia
75 øre I 5 gms (5 bre undepaid in fact)

Routing of letter
Air by ABA from Stockholm to Leuchars (Scotland); train to London (OAT added), by air, either via Lisbon or new Northern route to USA and on to to San Francisco and then by sea Australia. There was no civilian airmail to Australia at this time. It is possible it went by sea via Capetown to Australia, as the letter took I 0 weeks to arrive. The latter is less likely. One can only guess without transit markings!

(This letter comes from the Graff correspondence of private “under cover” mail containing letters sent to their son in Australia from German Jews, Benno & Bianca Graff, of Berlin and later Theresienstadt via family in Holland, Switzerland, Sweden and the USA to avoid the prohibition on mail from enemy countries – Torsten Weller). I possess a photocopy of the original letter in German.

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Airmail letter from Casablanca (Morocco) to Martinique with red type I cachet applied in London

Casablanca-BourselMaroc CDS of 4 August 1943

Fort-de-France 1 Martinique arrival cds (verso) dated 22 September 43

Censored
1. Casablanca and closed with brown tape and tied by Ouvert par I’ Autorite Militaire (verso)
2. London & closed using PC 90 tape marked Opened by Examiner 1482
3. Censure Militaire 1 Martinique 1 12 censor’s cachet (verso), but unopened this time

Postage – 1.50 Fr (≤ 20 gm)
Airmail to M’que – 17 Fr (≤ 5 gm)

Probable Route
Casablanca to Tangier by rail. Flown by Iberia from Tangier to Seville, Madrid and Lisbon (CAIS 191 of 10 Feb – wef 10 Jan). BOAC or KLM charter to Shannon. Shuttle flying boat from Shannon to Poole. To London by train (censored and OAT I cachet applied to top of 60 letter max bundle). BOAC northern route to New York via Foynes (Shannon), Gander & Shediac to New York. Train to Miami and then on Pan-Am’s Caribbean route to Martinique. The intended routing as paid was from Lisbon to go trans-Atlantic, not via London.

The letter took 7 weeks to arrive. Not bad when many flights were at weekly intervals and the queuing for censoring. London was keen to censor letters from previously Vichy French Colonies in an effort to learn anything, hence the routing via London.

This was a commercial letter between Banks.

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1943 Letter from Sydney to Sweden with red OAT type II cachet applied in London

7d was the correct rate for a sea mail letter to UK (3d postage) and then by air (+4d) to Sweden. The route is as discussed in figure 1. The %d war tax did not apply to a letter abroad. Had it gone by air from Los Angeles to Sweden, the cost would have been 216d per half oz.

Censored in Sydney and sealed with a closure bearing a red ‘2’ (verso). (Information courtesy of Richard Breckon)

The size of this OAT is on the low limits showing a new cachet (no solvent swelling yet). The postage date is some three months before Heifetz ERD for a type II. This may explain why!

The cds is difficult to read, which may explain its possible misreading previously and Heifetz dating. However, the month is quite legible. Heifetz is aware of my dating.

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June 1944 letter from Aden Camp to USA with violet OAT type II cachet applied in London

Correct airmail rate of 2 Rupees 6 Annas (2 x 3 A stamps verso) (courtesy of Gary Brown). Censored in Aden.

Probable route
In 1944 it was via Cairo, North Africa, Gibraltar to London (where OAT applied) and on to New York by Northern Atlantic route (Eire, Gander, Newfoundland). By this time Liberator planes were being used for mail. They had both greater load and fuel capacities for fewer stops.

Violet ink is much less common than red.

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1945 letter from Tel-Aviv to USA with red OAT type Ill cachet applied in London

Airmail rate to USA between September 1944 & June 1945 was 130 mils.

Probable route was via Cairo, Djerba (Tunisia), Gibraltar, London (OAT applied) and then Gander, Newfoundland to USA. By 1945, the Northern Atlantic route was available all year round to enable new planes to fly to UK from USA. (I also possess a violet OAT type Ill letter from South Africa to Sweden.)

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February 1945 letter from Johannesburg to Sweden with red type Ilia cachet applied in London

Airmail rate to Sweden was 1/6d per ½ 0z

Probable route. SAA or Sabena to Lagos via Leopoldville. BOAC landplanes along West African coast to Lisbon and Hurn or Bristol in UK. Train to London. In London OAT cachet applied for flight to Sweden, which was the only means of transport.

From London it went by rail to Scotland (either Prestwick or Leuchars) and thenwas flown to Stockholm by RAF or ABA across enemy occupied Norway.

These flights were nocturnal to avoid German aircraft, and went well north over the top of Norway.

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1944 letter from South Africa to Sweden with red OAT type IV cachet applied in London

Johannesburg roll-machine cancel of 21 Dec 1944.

Censored in Johannesburg and sealed with a bilingual closure.

Route was much the same as for first illustration. Now an airmail service was officially available to Sweden, for which the cost was 116d as franked.

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Sep 1945 letter from Switzerland to Australia with red OAT type V cachet applied in London

Postage was 30c with 70c airmail charge in 1945 making the 1 Fr paid. (Courtesy Torsten Weller)

From London the letter probably flew to San Francisco and then went by ship to Australia. The Horseshoe route was not yet open to ordinary mail, but the rate would have been higher and it should have been so endorsed.

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Aug 1945 letter from Jadotville to USA with red OAT type VI cachet applied in London

Postage 3.50 Fr and airmail to USA 12.50 Fr making 16 Fr paid.

Probable route. This letter went from Jadotville to Elisabethville by rail, and then to Leopoldville (28 Aug 45 backstamp) by air, and on as per the South African letters to London. Thence it flew by the Northern Atlantic route to Canada and USA.

Heifetz notes that t was thought that this cachet was a type V, which had been repaired. While the external dimensions may have changed, the enclosed letters should be the same size. They are not.

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Sep 1945 letter from Belgium to Australia with red OAT type VII cachet applied in London

Type VII is both the first of the new rectangular OAT cachets (21 Feb 45) and with type XI, that most seen.

Postage 3.50 Fr and airmail 14 Fr (5 – 10 gm from Brussels to New York) for 17.50 Fr paid.

Ms endorsement for air to New York.

It may have flown to San Francisco, due to the OAT, but then went by boat to Sydney. While the Horseshoe route was working again then, only airgraphs were carried then.

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Nov 1945 letter from Malaga, Spain, to Sweden with red OAT type VIII cachet applied in London

Postage of 75 centavos and 3 pesetas airmail for a letter ≤ 20 gm.

Sevilla (Seville) transit cds of 21 November (verso). It probably flew to Lisbon then air to London, where it received the OAT cachet. It may have flown directly to Stockholm being six months after VE Day probably from Northolt aerodrome.

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Airmail letter from Brussels to Yule Island (Papua) type IX OAT

Bruxelles-Brussel 14F cds dated 28 Nov 1945

Postage- 350 Fr (5 20 gm)
Airmail 10 Fr (5 5 gm)

Probable route. Brussels to London by air (BOAC). OATtype IX cachet applied in London. Airmail to New York via North Atlantic route of Greenland, Goose Bay and Montreal. Plane to San Francisco. FAM-19 route to Australia. From Sydney, it flew with QANTAS to Darwin and then Port Moresby. Road and boat to Yule island.

Airmail to Australia was re-instigated 1 December 1945 from Belgium via the USA with a rate of 10 Fr, rather than the 7 Fr to New York, which had operated since 23 March 1945, and which necessitated boat from the USA. Sender was alerted to this by paying the 10 Fr rate 3 days before its official introduction.

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December 1945 letter from Leopoldville to Detroit with red OAT type XI cachet applied in London

Postage 3.50 Fr, airmail to NY 37.50 Fr (3 x 12.50 F), airmail beyond NY 1.50 Fr (3 x 0.50 Fr), giving a total of 42.50 Fr for a letter of 10-15 gm weight.

Route similar to letters from South Africa, except that after the war, land based planes were used all the way.

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Airmail letter from Tangier to New York with violet OAT type XV cachet applied in Tangier

British Post Office / Tangier cds of 30 Aug 1946

Violet North Atlantic Service cachet

Postage to UK – 6d (5 ≤ ½ oz)
Postage UK to USA – 1/3d (≤ ½ oz)
Postage includes airmail

Probable route. Tangier to Gibraltar with TAE (Spanish). Gibraltar to Hurn (Bristol) with BOAC. Train to London for sorting and forwarding. BOAC to New York by North Atlantic route.

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1947 letter from Tetuan (Morocco) to Detroit with violet type XVI OAT cachet applied in Tangier

1/3 per ½ oz was the correct rate for 1947, so 1d underpaid. (Information from The British PO Service in Morocco 1907-57 pt III by David Stotter – kindly supplied by Tony Stanford in UK)

Type XVI cachet was used from 1942-1956 with main volumes recorded in 1947 (15), 1948 (29) & 1949 (10)

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Double weight airmail letter from Luneberg BAOR 8 area to Alabama with violet type XVII cachet applied in London

Field Post Office 463 cds of 14 Dec 1951 (from 5 Dec 51 – 1959, this British APO cds was used in Germany at BAOR 8 at Luneberg, near Hamburg) (Proud EB, History of BAPS vol 3)

Postage + airmail: 2/- (½ > oz wt ≤ 1)

(Rate was current from Jan 47 – May 52, confirming date of 1951) (Furfie, British Civilian Postal Rates of the 20th Century)

Probable route. By army postal service truck to Hamburg and military plane to London. The OAT type XVII cachet was applied at the Foreign Section of UK Post. From London by commercial airline to New York and by plane or train to Mobile. My thanks to Harold Sheath for his help with the postal rates.

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Airmail letter from Mkoani (Zanzibar) to Sweden with black OAT type XVIII applied in London

Mkoani cds of 9 May 1962

Postage – 50c (≤ ½ oz)
Airmail – 75c (≤ ½ oz)

Probable route. Mkoani (Pemba Island) to Dar Es Salaam by boat. Dar Es Salam to Kisumu via Mombassa with SRAS. Kisumu to Cairo with either BOAC or SAA.

Cairo to London on BA (successor to BOAC).

Black OAT XVI11 cachet applied at the London Foreign Sorting Office (small print below OAT is FS). Scandinavian Air to Stockholm.

Notes
1. Pemba island was noted for its clove growing and, then, did not have any landing strips, being very rugged terrain.
2. While Mombassa (Kenya) is closer to Mkoani than Dar Es Salaam, the latter is Zanzibar’s capital and thus the letter would almost certainly have gone there.

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Letter from Bahrain to Nova Scotia, Canada with violet OAT type XIX

Bahrain cds of 1 Apr 1965

Postage – 30 np (≤ ½ oz)

Probable route. Bahrain to London by sea. Violet OAT cachet applied at the London Foreign Sorting Office (FS for Foreign Sorting office). Pan-Am or BA to Montreal. Air Canada to Nova Scotia.

Notes.
1. Postage of 30 np (new pence) was for surface mail. Airmail letter rate was 100 np, while second class airmail was 40 np.
2. An interesting case, where the letter was paid to go seamail and yet was uprated in London. Maybe a sign of things to come, where nearly all first class mail today is airmail. The letter was also after partially paid airmail postage had ended (1952), although it was still embraced in second class, but without the ability to specify which portion of the journey was airmail.

To end, probably the most extraordinary use of an OAT cachet, where it was used as a canceller.

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Letter from St Albans to London & resent registered airmail from Grenada to London

St. Albans / Herts mechanical canceller of 22 Jan 1946 (under 2/- Grenada stamps)
GPO Grenada BWI cds of 25 Feb 1946 (also 3 verso)
Registration GPO / Trinidad transit cds of 27 Feb 46 (verso) Red R & boxed Registered Z8930 dated 27 Feb 46
Black OAT applied London as canceller for stamps
North Atlantic Service cachet in blue and m/s pencil
1. Postage (UK) 2½ d (≤ 2 oz) (2d orange & ½d green stamps)
2. All up rate to UK 2/7d per ½ oz (28 Jul 45 – 16 Jul 46) Registration 3d

Probable route. From London to Grenada in another envelope. From Grenada to Trinidad by boat. Registered at Trinidad (presumably money paid at Grenada). Pan-Am FAM-22 from Port of Spain to Miami. Miami to New York by train. BOAC North Atlantic Service) from New York via Gander to Blackpool. Train to London. This black OAT use is rare if not unique. No other BWI letter is currently known with an OAT cachet.

One other letter sent in 1943 from Grenada has 4/- franking, but nobody, with whom I corresponded, could shed light on the rate or why this letter was used twice. This letter should have been franked at 2/10d rather than 4/-. There is a note on the back of this letter that it was empty when opened in a solicitor’s presence.

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References
1. OAT and AV2 Markings (3rd Ed.), Murray Heifetz, American Airmail Society, 2006
2. Airmail Operations during WW2, Thomas Boyle Jnr, American Airmail Society, 1998
3. Extracts from the Air Ministry Civil Aviation Intelligence Report Summaries 39-45, Peter Wingent, 2010
4. Numerous private correspondences

My thanks to all those, who have helped me with rates and routes for letters with OAT markings. I would be interested to view any OAT or AV2 material, which readers possess & may be for sale.