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. Looks like it saw British and Canadian service in WWI and WWII. The BNP proofs seem to be added when pistol is sold off as redundant. From what I can determine from Birmingham Proof Mark Chart below the mark going clockwise looks like B (3 o'clock)-4(6 o'clock)-J(9 o'clock) which would indicate it was proofed in 1958. Also it seems the 1914 Canadian Government Model pistols were shipped with just one unmarked two-toned blue lanyard loop magazine normally supplied with Colt Government Model pistols due to necessity to get the pistols supplied quickly to the Canadian Expeditionary Force and later in 1915 spare magazines were ordered and marked with the C-Broad Arrow mark. According to a reply received from the Imperial War Museum in London: "During the autumn of 1914, the Canadian Government purchased 5,000 Colt M1911 pistols to equip its military forces. These were issued to officers, NCOs and cavalry troopers, but could also be purchased by officers wishing to acquire their sidearm permanently. Unfortunately, apart from a few pistols that received unit marks on the grip-strap, or were inscribed with the name of the officer who purchased them, there is no way of ascertaining which unit or formation they were issued to. I can’t see very clearly from your photos, but it appears that the proof mark on it post-dates the First World War. This would imply that the pistol was put through proof at Birmingham at some point after its First World War military career – and prior to it re-crossing the Atlantic."