Wadewade
The Model 15 with the 2" barrel is a fine little revolver and highly thought of by those of us who love the Combat Masterpiece generally.
The picture shows an interesting combination. If this is actually a Model 15-4, as your title suggests, the stocks are older than the gun. The -4 wasn't released until 1977, and PC diamond stocks were phased out by about 1967 (Change Order #937, issued on October 11, 1965). Hence, the stocks are a bonus on an already below-market purchase price. Congrats.