Well, none of these 'Thumbnails' enlarge if 'clicked' on.
What is the Serial Number? ( Last digits as "X"s is fine ).
In WWI, England had various Purchasing Agents for acquiring American Arms and may also have made purchases directly, I can not recall off hand on the latter.
Sometimes there were blocks of Serial Numbers, other times it was piece meal.
Your Colt is a Government Model ( rather then an m1911 ) which had been heavily buffed and refinished sometime along the way, and which has later or likely aftermarket Stocks.
Magazine appears to be correct.
Is the Barrel stamped ".455"?
And are there any British 'proofs' anywhere?
The "R.A.F." began in Aril of 1918 if memory serves.
I myself had supposed that most Country's WWI Aviators had usuaully carried their own private Purchase Arms, which would of course then have no Organization Stamps.
Your Pistol's serial number would allow some fairly close idea of when in what year, it had been made.
The Round Lanyard Loop on the Receiver is not Colt so far as I know, but is a nice one, and likely was installed back when.
I am not able to open any additional internet pages at the moment, to verify, but, if memory serve, the .455 Webley Automatic Cartridge was a little chubbier than the .45 ACP Cartridge, thus making for difficulty or disappointment, if trying to interchange the two.
