1 of 2 unknown coins found today - ID help please

[angifogg]

Please help to ID this coin found today. Is this a trade token? How would you go about cleaning a coin like this?

Thanks for your help

 

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[boris]

soak in olive oil a long time.

 

[testing123]

Or maybe some mineral oil. Careful not to lose any of that layer you see. That's probably your only hope at identification

 

[cbac]

From the notch on that it might be a knockout slug from an electrical panel.
Can't tell much without a size reference.

 

[Swartzie]

I've put mine in boiling peroxide for a minute or two. Looks like a large copper. If you have a pair of calipers take a measurement of the diameter. !/2 cents are around 23-24 mm and large cents aroun 28-29 mm.

-Swartzie