I am not sure, but the picture makes it look like this is a glue spot on the half. A soak in acetone (which cannot hurt the metal of the coin) would remove it if it is.
Also, since you like varieties, let me offer you the "cheat sheet" I used when roll searching halves. It took awhile and several references online and in print to compile this list.
Keep us posted what you find!
- When I value " being right
" more than what IS
right, I am then right...a fool.
- How much squash could a Sasquatch squash if a Sasquatch would squash squash?
- Real men play Fizzbin.