I think it might be awkward to keep loose caps in a hole in your stock, and would prefer to use a proper sized straight line capper for that task.

This little accessory was more likely intended to store a jag, worm, or a couple spare nipples.

I'm wondering if the maker of this little item started out with a rectangular piece of German silver, or actually drilled the hinge pin holes into the curved surfaces without having the bit wander all over the place.

Voting for anti-gun Democrats is dumber than giving treats to a dog that shits on a Persian Rug