Welcome! This is a .38 Military & Police Airweight from 1977; it may be stamped MOD 12-2 or -3 on the frame under the barrel with the cylinder out. It has an aluminum alloy frame and steel barrel and cylinder. It appears to have either dirt or corrosion on the barrel top; if the finish is damaged it is probably a $300-350 gun. Hope this is helpful.
Alan nailed it. Model 12 from 1977, either a -2 or -3, depending on where the gas ring is located. Easiest way to tell is by looking on the frame in the yoke cut, as Alan suggested.
Whatever you do, hang onto those stocks. Model 10 stocks will not fit your revolver.