Can anyone identify this very worn coin?

I found this coin in a field in Scotland. I can vaguely make out a small crown at the top but having real difficulty identifying what it is. Can anyone make out more than I can or tell me what it is? The other side is so worn there are no identifying features left. Many thanks 

Looks like a button

Indeed looks like a button.

Or maybe a coin that was used as a button. We could search the catalog for non-precious coins with that diameter but you didn't provided this information.

 Second picture has either PLATED or PATENT lettering, so yes a button 

from which the welded hook broke off. 

Thanks for your help everyone. Obvious amateur here so appreciate the insight 😁