Looks like a five screw S&W Model of 1905 4th change M&P with target sights to me. It has transitional grips, the long throw action, an adjustable rear sight and a partridge front sight. The extractor rod end tells me it left the factory after 1930, but prior to October 1946. The simple "Made in USA" mark tells me it left the factory prior to May, 1948. The hammer pin seen extending through the frame underneath the cylinder release was phased out around 1950 as frames were used up. If a target M&P was ordered after WWII, a pre-war frame milled for target sights may have been used. This is why
lettering the gun is so important. FWIW, the rear sight looks 100% correct in the photos. The K-38 Target Masterpiece came out in 1946, and it is hard to imagine anyone ordering a Target M&P after it came out, but I suppose it's possible.
The serial number will tell the real story. The serial number (on the butt) may have an "S" prefix, possibly a low "C" prefix. If so, it's a post-war transitional gun. If the serial number has no letter prefix, it's pre-war. It does have the unusual humpback hammer. This is an unusual and desirable variant. I suspect this gun wears the original grips and the original blue. Because I suspect original blue and grips, I also suspect the sight configuration is factory. These were special order revolvers, both in the sight configuration and the hammer configuration.
As a generic fixed sighted pre-war M&P, in this condition, it would be worth around $450. As a regular old post-war transitional M&P, it would easily be worth $300. If the sights are not factory, it is still interesting, and I would pay that much......If the sights are factory, you are looking at about $800-900 depending on who's buying and who's selling. If the sights
letter to the gun as factory, then you came out of the deal beautifully, and will own a very nice, unusual revolver.
Be careful you do not lose a friend in this deal. Good friends are worth more than money or guns.