I got the side plate off, and I found 22600 in a cutout on the inner surface of the side plate. That is the same as the number on the yoke and on the frame cutout behind the yoke.

I also removed the grips again. On the left edges of the grip frame under the grips, I see a small diamond, and the numbers 61, L2, and 866 in different locations.

The head of the ejector knob does seem to have been blued. I still think that other parts of the gun do not show signs of rebluing, because the edges and corners of the all the lettering look really sharp.

There are still a lot of questions. Could it be that the grip frame, cylinder, and barrel from an old WW1 era Army gun were put on a newer gun for the lend lease program in WW2?

Would a S&W history letter tell me anything about the number 22600, or would they refer only to the Army number - 150683?