While there are always a few exceptions, and in this case, very, very, very few exceptions, yes, the they were case hardened for blue AND nickel revolvers, of all frame sizes.
Thanks- I've had this revolver for years and to be honest never gave it much thought. I just happened to look at it this am and thought it odd that the hammer was in the white and the trigger was blued. I say odd because the revolver doesn't appear to be refinished- all the proofs are clear and sharp and there is the typical high edge blue wear as well as slight blue wear at the muzzle.
I suppose the hammer and trigger could have been replaced of some reason. I will say that the gun's action is like a bank vault- tight and precise- and seems to have had little use. The serial numbers appear to match.
Here are a few photos of it in natural light- thanks again for any information.
Rblue
Can you post a pic of the sideplate? That is usually the easiest place to spot a refinish. None of the tell-tale signs jump out at me in your pics. It's always possible that only the hammer and trigger were blued by some shop or swapped out. I've only heard of one special order that specified a nickel plated hammer and trigger for a Registered Magnum I think. I think it was destined to be engraved. Odds are high against anyone requesting a blued hammer and trigger on a basic M&P. I doubt the factory would have even considered it.
Age is mid to late 1921. The trigger definitely has been blued, who knows why at this point. The sides of the hammer ave been flat polished, you can see vertical striae on the flat, which still seems to show some pitting, which is probably why the hammer and trigger were blued at some time.
My money would be on the gun has not been re-finished, with the exception of the hammer and trigger. There are some people who seem to believe that the case-colored finish on these parts is someway a defective blue and don't like the appearance. Maybe that is why they were blued!