Patents: feb 6, 06. Sept 14, 09. Dec 29,14. Serial # 593870
I'd like to see more detail. It shares characteristics of the twenties and thirties, may be transitional or assembled from parts. No collector value. Practical value? Restoration, absolutely not. About the best solution is go to the auto parts store, get a can of Mother's Mag Polish. Remove those Franzite (replacement) Grips and rub it down to a combination of nickel and bare metal. That will take a while.
If the bore survives there may be a shooter hiding in there. At 4 million plus and counting it would be cheaper to by a used M&P than restore one.