As Greg says, quite rightly, 1925 to 1954 with those proof marks. I did look for the small mark that gives the date by way of a letter code. I couldn't see it so suspect that we can narrow it down to after 1941 and before 1950 when thay dropped that system for a few years. I've only got a bit on Cashmore serial numbers and dates but if my asumption is right it should be in the 19,000 to 20,000 range. Nice gun. Lagopus.....