Check with Numerich Arms for any missing parts if needed and they do carry schematics for alot of firearms , for referance. I am venturing a guess of a Mark IV Webley in .45 caliber from your info. Looked at one awhile back, a conversion done so they would sell on the U.S. market. I was told to keep the loads mild as some of them were prone to come apart from to much pressure of the .45 round. Same diameter as the .455 webley round but the rear face of the cylinder was machined so you could drop in " moon clips " with the .45 rounds and that is where the extra pressure came from, the .45 acp round is abit hotter then the .455. FWIW, hope this helps, still a neat gun cuz of the mechanical design.