Sorry, I posted this in the wrong forum. SN is either 604XX or 804XX. I think the former...the number is very small in the yoke, and followed by S&W. It's unaltered, pretty sure original bluing, and the side plate screws do not appear to be damaged.
On the butt is US Army Model of 1917, and below the lanyard ring is No (o is underlined) 84, and below that is 014, whatever that means. This appears to be in the same serif font, though smaller, as the info above it.
It's in pretty good shape; don't know the history of it. Seems to be original. Here's a view of the right side showing the side plate screws;