Close up of barrel markings indicate calibre .455 Webley self-loading cartridge, broad arrow Britishmilitary property mark; brass length of .900 inches and 9 tons/square inch pressure. Also shown is a .455 Eley magazine for these pistols. These magazines are scare and expensive; one just sold on Gunbroker for $200; recent going prices for such magazines I've seen are around $300-plus. They are available every now and then but you have to look for them; good places to look are Ebay; Gunbroker and AuctionArms and even some of the For Sale sections of various Milsurp and Colt gun forums. Over the past few years I managed to get several of these magazines.