I'll bet it's a Brinks gun. They sold or traded in a bunch of 2" and 4" 64s a while back and they've been showing up at great prices ever since. I snagged one with the lock for a very nice price a while back, but I traded it for a BNIB 10-22 Takedown... the lock and bobbed hammer just didn't scream "keeper!" to me. I still have a 64-3 4", 64-4 2" and 64-5 3" in the safe, though.