Here for your perusal is Colt .45 ACP 1914 Government Model Pistol serial number C9591 which was 1 of 20 shipped to Remington Arms-UMC Company Bridgeport CT on October 5 1914. The Canadian C broad arrow property mark is stamped on the magazine floor plate and British Birmingham commercial proofing on the slide and barrel.
A few more photos to show details:
Enlarged Canfield letter:
https://www.usmilitariaforum.com/for...4abb169119.png
The barrel is a U.S. military replacement barrel. Those barrel markings were first used in 1937. The original barrel would be polished bright on the chamber.
The British proofs are post 1955. Mr. Canfield noted that the pistol had to be commercially proofed before leaving the country, which is partially true. The pistol had to be proofed before it could be sold commercially in England, whether it was leaving the country or not.