its small like a US nickel and very thin. the obverse appears to have a bust of a man with a crown facing left and what looks like III to the right of his head.
Here are the other Pence coins for comparison I want to share these images with you from the Numista website
Spink : 3325 Monarch : Charles II Denomination : Threepence Issue : 3rd Issue Obv : CAROLUS II D G MAG BRIT FRAN ET HIB REX Rev : CHRISTO AUSPICE REGNO Description : With Inner circles and mark of value, mm Crown both sides Mint : mm Crown 1660-1662