The "standard" 12-gauge field loads with 1- or 1 1/8-ounce of shot came in the 2 5/8-inch shell, but from 1907 onwards our ammunition manufacturers only put the 1 1/4-ounce loads in 2 3/4-inch or longer shells and "trap loads" whether 1 1/8- or 1 1/4-ounce came in 2 3/4-inch shells.
That said, the 12-gauge Parker Bros. hang-tags I've managed to save pictures of are very confusing, several showing targeting with 1 1/4-ounce and saying "Use Shells 2 5/8" --
213855 12-gauge, 2 5-8-inch, 1 1-4 ounce.jpg
Others do show 2 3/4-inch shells --
108998 12-gauge, 2 3-4 inch, 1 1-4 ounce.jpeg
or targeting with 1 1/8-ounce and "Use Shells 2 5/8" --
211184 12-gauge, 2 5-8 inch, 1 1-8 ounce.jpg
214724 01 12-ga 2 5-8 inch.jpg
Threaded Mode