Flat Button ID Help

[smitty99er]

Please help me ID this flat metal piece. Possibly a button or small candle holder, but not sure from the shank in the back part. Thanks in advance.

 

[smitty99er]

Found at an Indiana elementary school in a town incorporated in 1830.

 

[rreahard]

what size is it? Kinda looks like a button off an old pair of jeans.

 

[smitty99er]

Here is a penny for reference.

 

[smitty99er]

I've cleaned it up a bit, but eroding of the metal has made it hard to identify any writing

 

[wolf-n-wa]

Looks more like a rivet or slate roofing brad.