Re: colt single action army
I can't be sure from just pictures, but many people who try to fake old guns have them plated with chrome, a cheaper metal than nickel, plus there are a lot of places doing chrome plating because of the auto restoration business, where not many do nickel.
Both metals have a silvery color, but chrome has a "cold" look, with bluish tinges, where nickel is "warmer" with more of a yellowish tinge. There is no real good way to explain except to have looked at a lot of guns and, I admit, sometimes I find it hard to tell the difference in some lights. But Colt did NOT chrome plate SAA's (or AFAIK anything else), so a chromed Colt is a refinished fake.