Bill Collingwood sent in a query related to the cover shown below
It has S13.1 Travellers cachet reported used Washington, but the Examiner's number 8186 is New York
It also has been datestamped at Bourne End Buckinghamshire on 28 September 1944
If it was a traveller's item it should have an American datestamp?
Quite a bit of what we do is, unfortunately, more-or-less educated guesswork. Despite a few trips to the National Archives long ago and the accumulation of a pile of TC covers, I am frequently still guessing. For better or worse, this is what I see here:
I am confident that the S13.1 attribution to DC is correct, based on the 2 covers shown in the census in the monograph which bear examiner numbers that were clearly used in DC.
The History of the Office of Censorship mentions that #s 8480-8484 and 8486-8490 were transferred from NY to the Chief Postal Censor's office in Washington, DC, to be used so as to make it appear that some mail transferred to that office was censored in NY. But the History says nothing about 8186.
As noted in my monograph, reports from the NY TC unit indicate that
5/6/43: Various numbers, 50XX / 82XX in TC Mobile Unit.
Note: for TCUs below, a later 1943 report changed and added some numbers. At end of 1943
new-series numbers appear. These are used along with the old-series numbers.
1/20/44: NY and Washington continue to use old #s in 1xxx, 5xxx, 6xxx & 7xxx series
2/8/44: NY starts using 216xx numbers + 6625; Washington uses 5xxx & 7xxx numbers
3/13/45: NY Customs House 21601, 21603-21605; La Guardia Airport 21602
3/13/45: Washington same numbers as before + 20 & 35
The covers recorded in the census in the TC monograph (Appendix G) include 8033 and 8915 used in the NY TCU and 8310 used in Philadelphia TCU (subordinate to NY TCU), so clearly there was more going on than the 1xxx, etc. and 82xx series reported above.
The History says nothing about NY transferring numbers from the 5000 and 7000 series to DC, suggesting that the 8480-8484 and 8486-8490 report refers only to those numbers transferred for use by the office of the Chief Postal Censor and not to any numbers used by the DC Traveler's Censorship Unit subordinate to NY.
So, given the presence of the S13.1 handstamp, my read is that this cover was pre-examined in accordance with the instructions shown in Appendix A, by the TCU at the Georgetown Customs office in DC, for a passenger bound for the UK, who then posted it when he got to his destination. It does not have a US postmark because it was not posted in the US.
Clearly it would be good if someone could get back to the National Archives and see if there are reports that I missed that fill in the gaps about which numbers were used by TC examiners. Until then, we can only build the data cover-by-cover, and hope that the guesses that we have to make are right.