I'm new here, so please bear with me, because I'm not afraid to ask questions, even basic ones. I have seen many, many references to "factory letters" on S&W revolvers, particularly collectible ones. What is the purpose/function of a "factory letter"? I just sent out the money order and FFL to a seller for a 1948 K38 Masterpiece - should I get a factory letter on it? From what I can pick up, a factory letter is like getting a genealogy report/family tree report. And I can't wait to get my "new" gun...