There's more that can be learned for some and clarified for others from Stan's pic of Bo Whoop's barrel flats . . . I have often read in posts concerning Fox barrel weights as only being 1-2-3-4. However, that's not totally accurate . . . from charts of factory blueprints dated 1912 McIntosh told us that the 20 gauges were given a slightly different number sequence---0-2-3-4, as opposed to the 1-2-3-4 sequence used for 12 and 16 gauges. McIntosh also went on to say that in about 1922, the factory added a fifth 12-ga. class, No. 0, for the Super Fox, as seen stamped on the barrels just ahead of the water table of Bo Whoop's barrels above.
