Artillery Trainer

I have a Remington and Peters .22 box with an Artillery Training overlabel.
The cartridges are a .22 Long blank, 0.0596 inches in length and a paper top wad that is recessed 0.115 inside the case mouth. The day lot code on the Remington box indicated it was made in 1947.

Cute box! Do you or does anybody know what these were used in??? I can’t imagine a 9x19mm Artillery Trainer round, much less one in .22 Long!

I am prepared to be amazed…