[..]

Are Kimber's black guns stainless underneath? What is the black finish?

[Monkeyleg]

Depends upon which Kimber you're looking at.

The Pro Carry series have an anodized steel slide with an anodized aluminum grip frame.

The Royal series pistols are all steel, and are traditionally blued, and to a high polish.

The Gold Match series (except, of course, for the stainless models) are blued, and all steel, with a high polish finish.

The Gold Combat series have the "Kim-Pro" finish (which I think is Gawdawful in appearance).

Recognize, of course, that Kimber produces a new model just about every week, so YMMV.

The Ten series pistols have a steel or stainless steel slide and a polymer frame.