It has to be nickel finish as I opened it up to check for rust under the handle and it is not toooo bad. but clean upable.

I had it check by local gun store. Actually it is 2 doors down from my office. 17 range lanes and a complete gun store. indoor.

And they assumed the same thing it is Nickel.

I sent an email to S&W "Tom" and I am waiting his reply. I will post that reply here when it arrives.