letter the gun refers to sending a request to the S&W historian (I think the fee is $50) to research the gun. they can tell you it's original configuration as it left the factory and wher it was shipped to. Most of the time these letters on recent production guns are pretty boring- like gun shipped to a large gun distributor or something. on occasion, it will reveal shipment to someplace out of the ordinary like a gov agency police department or overseas order.