I checked Kerksis last night, and though admittedly incomplete as virtually every known source is, there is not an example of this object. I still think it's a top to a small tin where the skirt has fallen away at the solder joint. Carefully looking at the reverse you'll see spots where it is rough; as well, the die that made it stamped down the outer-most perimeter of the piece on the reverse (which may acccomodate a skirt) which is the opposite proceedure you'd see if this was a mounted plate encompassed by a backing. It would be too early (15 stars) for percussion caps, but it could have held a number of other things for rifle or pistol, or even cheap snuff maybe. It's a very cool find, that's certain.