Which parts would have been hot blued on guns made prior to 1940 or so? I had the impression that the barrels were rust blued, the furniture was hot blued, and the frame was case colored. Is that incorrect?

I'm thinking primarily of British made guns, and it occurs to me that the answers could be geographically specific.

Follow up question: Is there any role for tempering screws to the color one wants? (I'm assuming that would not be a good idea for the actual furniture.)

Jim