There does appear to be one diamond on the frame, and one inside the barrel.

When we talked about it my best guess is that it's a commercial 1917 frame that went back to the factory after the Outdoorsman was introduced to have the barrel and sights added.

Then had the hammer/action job done to it by someone I don't recognize. The closest I have seen to that hammer is the one that Frank Pachmayr did on Elmer Keith's registered magnum.