Bob, from the little information you gave, and if the 4 digit number is the serial number, the gun was made late 1946 early 1947. The whole serial number would be helpful in dating it correctly. If the serial number is a 4 digit, the prefix would be FW S1000-S9999. The .410 first came out in 1926. As far as shooing modern shells I would have the gun checked by a good gunsmith first, but see no reason why 2 1/2" shells could not be used. Value is all in condition, the .410 now will bring 3-4 times more than a comparable 12 ga.