The receiver is a standard grade. The barrel may have same serial number, but not the barrel that came with the receiver when new. The barrel has engraved ears and came with a higher grade M32. Someone has renumbered the barrel to receiver.
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.