That looks like a really cool button find! Congrats. Is it 2 piece or one piece? I found one with a similar coil attached to the shank. Lots of debate on what it was for. I'm going with that it was some kind of extra thing to keep it attached in rough conditions.
The metal coil is what held it in place on a marine dress uniform. The metal ring had to be removed for the button to be taken off of the uniform and polished. Semper Fi!
RJGMC