Fox Collectors

Can somebody explain the barrel weight numbers stamped on Fox Guns?

Fox assigned numbers for unstruck barrel weight, these numbers are stamped onto the bottom of the barrel just forward of the barrel flats. Often they are not visible having been removed during the striking process. For 12-ga. and 16-ga. barrels these numbers were 1,2,3 and 4, with 4 being the lightest. For 20-ga. barrels the numbers were 0,2,3 and 4 with 4 again the lightest.