I have my father's 629-4 Classic, and he had a scope on it, rear sight is missing. I can't exactly ask him anymore since he passed away (thus why I have the .44). I want to get the hard rear sights, and I looked at the ones at Brownells and called them up to verify, and the guy on the phone said there is a new and an old style, and he can't get the old style anymore. Now, I can't remember what he said about how to tell, but it was something about the front of the rear sight guide being rounded vs square. Can anybody verify this? Also, is there a way to tell by serial number?