I'm proud to show this exceptional (unique?) coin:
O/: CONSTAN-TINVSAVG [CONSTANTINVS AVG]; head r., with plain diadem, looking upwards. [CYZICUS 57].
R/: PROVIDEN-TIAECAESS [PROVIDENTIAE CAESS]; camp gate, two turrets, no doors, star above, varying number of stone layers. SMKS• in exergue [CYZICUS 37-38].
It proves that Providentiae type for Caesars (but certainly not for Crispus) was minted also during the second issue with m.m. SMKA• [CYZICUS 55-57], when Constantine's I bust changed from laureate to diademed.