My interest stems from the fact that I have my father's 1937 16 gauge, a well used but nice old gun. I am looking at an old 12 gauge that has a crosshatch, you might say checkered pattern on the sideplate. Looking up serial numbers, it could be 1920 or 1947. I'm thinking 1920. Dad's has an 'F' prefix to the number. If it's 1920, low pressure loads only. Can the experts enlighten me?