My 1903 UMC saleman's catalogue shows paper 12-gauge shells available in 2 5/8, 2 3/4, 2 7/8, 3, and 3 1/4 inch lengths. In addition to the above lengths, 12-gauge brass shells were also offered in a 2 1/2 inch length. However, you must remember that in those days, those longer shells were usually for more and better wadding, not a heavier shot load. The famous Widgeon Duck Club 3-inch 20-gauge shells of pre WW-I era were loaded with 2 1/2 drams equiv. and 7/8 ounces of shot, while the heaviest load in the 2 1/2 inch 20-gauge case was 2 1/4 drams equiv. and 7/8 ounce of shot.