Found on a Civil War battlefield in Maryland

I found this on a battlesite on South Mountain.  It was a couple of inches down.  It's made of brass and has a green patina.  It appears that it may have had a gold colored gild because some pieces are still there. Anyone seen one of these before or know what it belongs to?

Peepsight for a carbine?

It appears too thin to be a sight. I could bend it with two hands.

It has the look of a spacer of some kind; maybe on the pivot of a transit or something like that?

   If it still had the missing half of the ring like the other side....it sorta looks like part of a vintage automobile thermostat. The part does look dished in the pics to me. Thats my wag.....

TiredIron

part of the workings for an old tube type radio tuner?

Curiosity getter for sure.

   If it still had the missing half of the ring like the other side....it sorta looks like part of a vintage automobile thermostat. The part does look dished in the pics to me. Thats my wag.....

part of the workings for an old tube type radio tuner?

I thought about both of these... part of a dial face/frame.

Considering it looks like it's broken on one side, I think we can agree it used to look like this?

Mike you always find something different. Hope you guys have a Happy Thanksgiving.