Constantine I Ӕ Nummus. Treveri, AD 316. IMP CONSTANTINVS AVG, laureate and cuirassed bust right / MARTI CONSERVATORI, Mars standing right and looking left, helmeted in military dress, holding reversed spear and resting left hand on shield; T in left field, F in right field, BTR in exergue. RIC 117. 3.04g, 20mm, 12h.

Extremely Fine. Extremely Rare; no other examples on CoinArchives.

From the inventory of a UK dealer;
Ex Bourton on the Water Hoard, 1970.