Lew - I wonder if these weren’t meant to use a .22 blank as a primer, or maybe a .22 BB Cap with the ball pulled out, as a primer, and loaded with blackpowder and a real full size bullet. This would allow people to shoot their Spencers, etc., with live ammo (or homemade blanks for reenactments) in a rimfire gun where no modern ammo was available. Not the greatest solution, if I am correct, but I suppose better than nothing. Today, Starline makes a lot of the cases in center-fire, and there are cneter-fire breech=-blocks made for Spencers - hell, there are Spencers made in centerfire.
Just I thought. I really don’t know or have any ads or other documentation on these. Just a guess to get the ball rolling on identifying them.
For the purpose I describe, I would have simply made them to take standard primers off-set so the rimfire pin would hit them, but maybe that was not practical.
The main thing, is that the look like they were meant to take a standard bullets of the proper diameter for the original barrels in the calibers they are in.