M1911 was adopted by US Govt that year, and became commercially available right away. The first military serial numbers weren't used until early 1912, so you'd have to say that was when it was "released for combat," but folks started shooting each other with it just about right away.
All the early pistols were blued. The metal polish got pretty sloppy during World War I, but finish was still blue. Parkerizing didn't come into standard use until the early WW-II era. You see quite a few 1911s with Parkerized finish, but there are arsenal reworks of old guns.
Nickel plating was a standard option on commercial guns as of 1935. Special order finishes were available well before that. It was available on the 1903 and 1908 pocket pistols by about 1921.
Best,
RR
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