I recently inherited this Browning 20 gauge O/U and need help with the model information. It has a serial number 20XXX and I know it was purchased prior to 1970. The barrel says "Browning Arms Company, St. Louis MO. & Montreal PQ". I went to the Browning webpage but it seems that do not list any serial numbers prior to 1973 for O/U shotguns. Any help and an approx. vaule would be appreciated. Here are a few PICS