I thought K-Kote was only used on the nickel-looking pistols (in lieu of a stainless finish, before stainless came out on Sigs)?
I've read elsewhere that K-Kote's durability is suspect, and in some cases flakes off after moderate use.
Factory finishes I'm aware of, besides K-Kote: original "blued", blackened stainless slide, Nitron finished stainless slide.
Regards,