Marine pilots would have carried Navy revolvers. It is worthwhile to get a factory letter. See: http://www.smith-wesson.com/webapp/w...4_757812_image

The letter will establish that the revolver was shipped to the Navy and will provide the exact date it left the factory. It won't tell you anything beyond that, such as to whom it was issued. The letter costs $50, but it is worth it if/when you ever decide to sell it.