I have owned this coin for about ten years. It's sat unattributed in my collection. I've wondered if it might be an AE denarius of the British usurper Carausius.
It's not in the best of shape but I appears to have a laureate bust. It is 17 mm. in diameter and weighs 3.95 grams.

I found this link to a CNG auction for an AE Carausius denarius which bears some similarities to my coin.
https://www.cNGCoins.com/Coin.aspx?CoinID=136301Here is the coin from the CNG auction.

Finally, during my online research I came across this CCF post from two years ago.
http://goccf.com/t/342774Thoughts on this interesting coin are most welcome. Thank You.