Don and George,
I think that is a .44 Hand Ejector, Third Model (1926 Model). The three .44 HE models are nearly identical, but there were some slight interior changes, especially in the hammer and trigger and their spacing, as S&W kept monkeying with the DA trigger pull. I think the patent mark on the hammer was only in the third model, not the second. The third also had a hammer block and the hand was made to match it.
The hammer of the 1917 looks almost right, but I don't think it will fit, though you might try if you can find one.
As last resort, send back to S&W. They have been known to make a part from scratch if necessary, but maybe not any more.