The records show that Serial Numbers 51693 through 51728 (and in a few other places in the FWS numbers) were used twice. The first use of the number has an "A" suffix while there is no letter following the second use of the number. Using a serial number more than once is not uncommon. However, the FWS (Marlin) records are the only ones where an "A" is used on one of the pair. In the earlier books, occasionally three separate shotguns have the same number, and the three entries are crowded onto one line.