"... First off, let me ask -- is this common for coin finishes? I have never had a similar problem with stainless steel pistols, so I was a little surprised, although I am sure I have no one to blame but myself..."
Newlyn,
What this indicates is that your gun has a traditional "coin finish" on a traditional 'low alloy steel' used for most guns. Steels from "mild steel" and even "chromoly steels" are considered low alloy. They are subject to corrosion fairly quickly. Casehardening or deep thru (martensitic) hardening of these steels will increase their corrosion resistance, but not eliminate corrosion susceptability. Traditional "coin finishing" is typically casehardened steel that has been polished, but many other processes have been used to end up with this polished finish.
Stainless steel has high chromium and nickel content that makes it highly corrosion resistant and therefore you won't get that smutty gray corrosion from your hand acids and salts.
