Luxembourg aerophilately is a fascinating field full of unsolved mysteries. And one in particular—the scarcity of O.A.T. mail from Luxembourg—continues to evoke my curiosity. Surely somebody in Cyberland will be able to suggest an answer.
O.A.T. is the abbreviation for Onward Air Transmission. Various OAT postal markings are found on airmail that transited through the London foreign section and was to be carried onward by air through a series of intermediate points. According to Murray Heifetz (OAT and AV2 Markings, 2d ed., 2002), OAT markings were used from 1938 to 1974, although most are found on airmail posted during or in the aftermath of WWII.
The cover shown here would be sufficiently interesting simply because it shows a commercial use of the 1945 Thanks to the Allies semi-postal issue (valid only from March 1, 1945 to June 1, 1946), including the 2.50+3.50 fr. and 4.20+4.80 fr. high values. Commercial use of any of these semi-postals is seldom seen. However, what is even more intriguing about this cover is the bold boxed red oval O.A.T. marking, of which I’ve only seen one other example on airmail from Luxembourg.
The cover was posted from Luxembourg-Ville, October 19, 1945, to New York City, New York, USA, with the OAT marking presumably applied as the airmail letter transited through London en route to New York City. In addition to the four 1945 semi-postals, part of the postage is paid by a 10-franc 1944 Charlotte definitive (the high value of that series). At the time, the UPU letter rate was 3.50 fr. for the first 20 g plus an airmail surcharge to the United States of 7.00 fr. per 5 g. Thus the total postage for this six-gram letter amounted to 17.50 fr. The franking, which totals 18.50 fr., overpays that amount by one franc. The address and return address show that the letter was correspondence between members of the Salomon family, who were active in Luxembourg affairs, both in Luxembourg and the United States at the time.
As we frequently see airmail covers emanating from Luxembourg during the post-WWII era, why have I seen only a scant two with an OAT marking?