Rather an interesting old set of castings for a rail-mounted WW1 gun, 3 1/2 inch gauge mounted on bogies. Predominantly in aluminium, with bronze breech block and steel barrel. There are three set of wheels on axles ready turned, the remaining set is missing. Nicely detailed.
No drawings with this one, but a good copy of "Rail Gun" by Batchelor & Hogg giving much technical information and drawings of a wide range of rail-mounted artillery. The whole thing is housed in a fitted wooden case, which it appears to have been supplied in from new.
Overall length 30 inches