I measured the chamber length of this thing. They're right about 3 inches. So, a 2 3/4 inch shell would work. I'm thinking they are made for the American market. I read somewhere that English shells of the period were 2 1/2 inches.

Does anyone know anything about the locks? What type are they? Since there are screw ends showing behind the hammer there must be parts attached back there, so I'm guessing the main springs are forward of the hammer. You guys seem pretty knowledgeable about these things, can anybody shed some light on this?