Dear Raöph,

Thank you for contacting Mearto with your appraisal inquiry. My sincere apologies for the delay with the appraisal.

The presented object appears to be a quarter of a copper Ass coin made in the Roman Empire. The As was the smallest amount in the Roman coin system and sometimes they were cut into smaller pieces like in this case. (https://en.wikipedia.org/wiki/As_(Roman_coin)
The images of the coin are not visible so dating os not possible. It was made in the first four centuries after Christ.

Comparable objects were recently offered and sold on the international auction market.
This piece is in good condition and no severe damage is visible in the images provided.
A fair market estimation would be between 10 to 30 USD.
This estimate is based on actual recent past recorded auction sales of comparable items. Retail "asking prices" can be higher and may vary.

With kind regards,
Gregory