I don't think that gun is anywhere near as old as you think it is. It looks to be an M&P from the late 40's early 50's maybe. You didn't mention a prefix to the S/N but I'd bet it's a "C". C 143XXX puts it at the late 40's. That "C" or other letter is part of the S/N and makes a difference. If it was as old as you think, the ejector rod would have a "knob" on the end like this Third Model Hand Ejector 32.
View attachment 1200390
That gun looks like the 38 M&P I put on layaway yesterday. S/N is in the C 310XXX range, which puts it in the 54-56 range.
I'll show the same side. Ignore the stocks. They are some sort of no-name aftermarket, but don't look too bad.
View attachment 1200391
Might as well show the other side too.
Note the ejector rod end is like the one you pictured. This one is a five screw, which I suppose the one you pictured is also. I think I can see the front trigger guard screw in your picture, but that might just be that I expect to see it, so in my mind it's there.
The purple color isn't rare or anything, but it's not really common on Smith and Wesson's either. I had a Model 39-2 once that had a purple safety/decocker now that I think on it. If it really is from the early post-war period, it's possible that a batch of blue solution wasn't quite right, or the steel was different. A lot of GI's were returning to the work force after the war. Some may have worked for Smith and Wesson before the war, or they might be in the same boat as a lot of other people, then and now, just starting off learning a job. Things happen. Smith and Wesson after the war continued to use a finish similar to the wartime finish to speed up production to catch up with the demand for civilian guns that had been building up during the war years when everything was going to the military. It would be at least ten years from VJ day before they really got back to the bright blue we think of when we think of Smith and Wesson across the line.
Is it worth $700? Not to me. For $700 I'd be thinking, in like new condition, with box and papers. I put the one above on layaway for $450. It was tagged at $499.99. It's far from immaculate. It's got some minor rust issues, nothing Flitz and Ren Wax won't take care of, and of course, we mentioned the stocks, but mechanically it's good to go. Lockup tight, times right, bore bright and shiny. It's got a SS number scratched into the bottom of the grip, I forget which one off the top of my head, and a number stamped into the grip. Probably a rack or badge number. Neatly done and I just look at it, and SS number, as part of the history. Another gun I'd like to sit down with a cup of coffee, flip it over in my hand a few times and say, "Now, tell me your story."