On the bottom of the monoblock there will be a Roman numeral stamp. I, II, IV, etc. that will tell you the grade of the engraving on the barrel. It’s quite common to see a II (San Remo) engraved barrel on a I (standard) grade gun. A lot of these barrels were fitted in Miami (Europa Corp) back in the day and not at the factory. Hence the barrel is correctly serial numbered to the gun.