"I was just wondering it there would have been any quick visual indicators (other than knowledge of serial numbers) that would have given it away a post war."

You can see part of the 1945 improved drop safety mechanism if you look into the hammer well. There have been pictures here of postwar M&P RB snubbies with original black hard rubber stocks. I have yet to personally see one of them. I think that would be the "coolest" option for yours. By the way, the "Model of 1905" terminology was dropped by S&W prior to WWI, when they started calling them M&Ps (round butt and square butt), but its use has continued among some collectors to describe M&Ps made until the Victory series started in 1942. By any criteria, yours is an M&P, not a Model of 1905.

I have on my list quite a few S-series M&Ps having nearby SNs on both sides, all of which shipped in the October-November 1947 period. But a factory letter would be necessary if you need a more exact shipping date. $350 is a super price.