...well, not quite half...lower part of a musket butt plate. I love finding gun parts and a butt plate is one I am still trying to knock off the list...so far just bits and pieces.
I don't think any of my pieces are much larger than your pieces , but I'm still looking for a larger chunk, one of these days the whole one will pop out!
Not an easy find, but not an impossible one either, keep at it