Blowing up the pictures with the holster the gun does not show any indications of being re-finished. The factory date-code and re-work star indicate that something was done to it in 1949. What would be definitive is if there is an indication of "cratering", a raised burr, around the star on the butt. If the gun has not been re-finished since that stamp was applied this will be obvious. If it is polished smooth the gun was re-finished after the star was applied.

Again, blowing up the picture it appears this gun has the hardened inserts in the cylinder stop notches. This is characteristic of only very early hand-ejectors and ended about 1906 or so. Are the inserts there?

Both Vintage Gun Grips and N.C. Ordnance insist they do not make a reproduction stock for a M&P, unfortunately. This one, S & W Perfected Model .38 Revolver , may work. It is for the "Perfected Model which was a hinged frame revolver built on what appears to be the M&P frame.

FWIW, the Military & Police markings have nothing to do with your Grandfather owning it while he was in ROTC. S&W designated the model as M&P, and Eubank marked the holster to indicate it was intended to fit that model, nothing more.

Eubank Leather later became Idaho Leather and made very well thought of holsters. The company is still in Boise, although under different ownership, and still makes the old-style basket stamped, laced and 1/2 lined holsters they were well known for for many years. They are all custom work now, and definitely do not sell for $6-8 like they did in the 1960s.