I'm also not so sure any part of that gun is stainless. The slide looks like it has the two-piece roll pins SIG used on folded carbon steel slides, and I think I can make out a separate breech block on the top of the slide behind the ejection port, instead of the integrated breech block machined into a stainless slide.
Also, I can't quite make out the serial number, but the frame looks like one from before SIG ever made frames from stainless steel.
I think that is a nickel gun where the finish has deteriorated.
Last edited by wgsigs; September 17, 2012 at 08:04 PM.