I think that you have a Victor Sarasqueta, imported by Stoeger in the 50's. There should be a diamond with a running hare stamped on the water tables. If so, you have a true sidelock and a hell of a good gun. My 20 bore was made in the 50's and I have not had a single issue with it other than broken firing pins which are easily made of tool steel rods of the correct diameter and an electric drill. Good find. Chops