My apologies, Jim, for the scant info. This is what I think (but don't know):
I believe it to be a 45 Hand Ejector Model of 1917.
It is a commercial model (with S&W medallions and no military markings), not Brazilian contract, and made sometime prior to the hammer block addition.
It is stepped to headspace the .45ACP and should also chamber the .45RIM.
No moon clips were offered with it and it has no lanyard ring (although the hole is there for it). It is an interesting gun, to me, so I paid the asking price and took it home. I had time to take only one pic.
It is marked DA 45 on the right side of the barrel, S&W etc, with patent marking on the top of the barrel, and Smith & Wesson on the left side of the barrel. The underside of the barrel (under the ejector rod) is marked with the serial number and, separate from the serial number, but nearby, a diamond with an S.
All serial numbers match; frame (marked on the butt), cylinder, and barrel. There is no prefix.
Don't know when it was made (although probably sometime between 1938 and 1948) nor what the value might be (which interests me for long-term collector status and support for my wife, if I decide to cross over before she does
). So, I would be interested in learning what I could about it.
Addendum: There are some quite tiny markings on the frame under the crane where later model numbers were placed. I haven't yet been able to read them.
Thanks, again.
Will