Well the best I could tell from the pictures is it looks to be Belgian post 1952. Both controllers listed on this gun held proofs in 1952. There looks to be a really faint date code on the gun. If it is the correct one it would make it a 1953 piece. Which would fall into the timeline of hoth the below listed controllers.
Controller of Proof - Daenen Charles 1952-1968
Controller of Proof - Laenen Clement 1952-1986
Best I could do with the pictures of the gun. Try to find pictures of what other guns similar to yours are selling for to get a value, if you can find any.
