I would never have found a SD-40 if I were in search of one. Spotted this one on a table at a recent gun show. While looking it over, the seller told me "it's an experimental pistol, and that's all I know". Wasn't exactly sure what he was meaning, but he did mention the very low serial number, so I'm guessing that it had something to do with his statement. I didn't question him and paid his price. Came with the original PC case, mags, paperwork, SAT, and what I'm assuming to be a partial remnant of the end label stuck to the top of the case.
Little info is available because of the model's rarity, but I have found several good threads....including this one. Post #16 by Sevens is gold!
S&W Performance Center Stocking Dealer SD9 and SD40