It looks nickel to me, and probably doesn't have a groove for the pin as it's after 1982??As you know, the same with me. I did see on ebay a 6.5 bbl in S.S. but I'm pretty dubious. It's pretty shiny and the text on the barrel doesn't look right to me. Take a gander and see what you think. item #256129721423
As far as I know Smith never made a 6.5 Stainless bbl for the 629.
Rick
I'd need more pictures