Roman campgate folles, but as to which one, you need to post the obverse. Here is an example:
Roman Imperial: Constantine II (326-327 CE) AE3 Folles, Cyzicus (RIC VII-47)
Obv:
CONSTANTINVS IVN NOB C; laureate, draped, cuirassed bust of Constantine II facing left
Rev:
PROVIDEN-TIAE CAESS; campgate, 2 turrets, 6 layers, star above, no doors. Mintmark: • SMK Γ •