You will be surprised at how much gun you got for your money! The finish, which looks like stainless, is not stainless. It's some kind of coating or finish treatment to carbon steel, from what I understand. It must be proprietary because apparently EAA/Tanfoglio really doesn't disclose what it is.
As noted above, they are good, solid, inexpensive guns in their low-end variations, and quite sophisticated and refined in the more expensive models. The only downside is that EAA's customer service doesn't have the best reputation. You'll probably never have an issue. (You must pay for shipping to and from the factory if you have a warranty problem, and that's a negative.)
EAA has Witness models available in a semi-gloss Blue finish (which is common on the least expensive models - I've had several), a Wonder Finish in Blue, a Wonder Finish in Silver, and also in (hard) CHROME. IF it looks like stainless, it could be Wonder Finish or Hard Chrome. (If you bought a gun with the hard chrome finish, you'd probably know it,as that frame (not a finish) is generally only seen on the more expensive models.)
Technically, EAA says Wonder Finish isn't really a finish, but a surface hardening treatment -- apparently applied before it receives the color application. Wonder Finish, according to the user manual, must be treated just like carbon steel; it can rust if ignored too much... and I've seen photos of some silver ones that were ignored too much.