I have both a shell and a bolt of this style, was told that they were end-of-war/postwar unfired, they were referred to as Staffords/Arricks/Eurekas and that they were designed to take a Hotchkiss style fuse. Also, they were sold by Bannerman's. I also have an identical shell but without the bolt and have been told that it is a Stafford/Arrick/Eureka, so I'm not really sure what they are.