Sorry, sgms, that is not a cup fire cartridge, it is a standard Benet primer, of the type used for many years by the U.S. Army for both rifle/carbine and pistol ammo. When the Custer battlefield site was first researched, fired Benet cases turned up and some researchers, unfamiliar with the guns and ammunition used, thought they were rimfire rounds. A few noticed the firing pin dents in the center and reached the weird conclusion that there was some kind of conspiracy in the Army to issue rimfire cartridges even though the soldiers' weapons were center fire! Talk about ignorance leading to conspiracy theories!!
The cup fire cartridge, like the teat fire, was loaded from the front of the revolver (Plant) cylinder. The chamber was not drilled through but had a hole at the back through which the hammer struck down onto the side bottom of the deep crater in the rear of the cartridge. That contained the primer. I have not been able to obtain a good picture of a cup fire round, but will keep trying. If you Google "cup fire cartridge", though, you will find some good pictures and diagrams.
The "teat" of the teat fire cartridge contained the priming compound. The hammer struck down onto the teat, firing the primer. The revolver that used them was the Moore, and they turn up fairly often at the larger gun shows. I bought one at Baltimore a couple of years ago, but was not successful in my request that the seller just throw in a box of ammo!
Jim
P.S. Here is a good source with pics and descriptions;
www.cartridgecollectors.org/?page=glossary
JK