If it is a .38 special m&p then those are tough to nail down unless somebody got a letter for a gun fairly close to your number. They started in 1915 with #241704 and went all the way to 1942 with #700000 But I would say 1915 or 1916 on yours. Should have service stock with gold medallions for grips and if you check under right side grip you may have your serial written there in pencil.