Very cool!!
Do keep in mind that they weren't made for the modern day 3 1/4-dram equiv., 1 1/4-ounce of shot, 20-gauge 3-inch Magnum shells. Before WW-I, when they were made, the 20-gauge 3-inch shell carried a maximum load of 2 1/2-drams of bulk smokeless powder or 20-grains of dense smokeless powder such as Infallible or Ballistite, pushing 7/8-ounce of shot.