The barrel shown in your photos has the correct (and only) address stamped on squareback 1851s. It is distinctive because all squarebacks had the "NEW YORK CITY" address. Walnut grips as opposed to.....? Walnut was the standard grip material. Special orders were available with ivory, bone, etc. Hard rubber was never used. I believe that all the numerals in all serial numbers were stamped with individual dies.