Magnus Maximus AE4. 

Obv: DN MAG MAXI-MVS PF AVG, pearl-diademed, draped & cuirassed bust right 
Rev: SPES RO-MA-NORVM, campgate, 2 turrets, 5 layers, star above, no doors; 
Mintmark: PCON

Arles mint. Not in RIC with pearl-diadem (RIC describes the
headwear as "plain diadem".

Bishops Cannings hoard, no. 1033, rated rare