Flavius Julius Crispus was the eldest son of Constantine. He was made Caesar in AD 317 and defeated the Germans in AD 320 in Gaul, the same year of Constantine's 15th anniversary and is commemmorated on the reverse of the coin above - a reverse type that came into use in AD 321. Crispus entered his second consulate in the same year and celebrated his quinquennalia in Sirmium. He commanded the fleet against Licinius and celebrated his decennalia in AD 325. En route to the West Crispus was executed in northern Italy the next year.

Obv. Crispus facing left, holding spear and shield, IVL. CRISPVS NOB. CAES.
Rev. Globe on altar indicates that the world is at peace, inscribed VOTIS XX, the legend reads BEATA TRANQVILLITAS (the blessed tranquillity), PTR in exergue.

This coin with the reverse type of a turreted gateway comes from a later series struck spesifically for Constantine and his sons Crispus and Constantine II.

Obv. Crispus laureate, draped, cuir. bust left, FL. IVL. CRISPVS NOB. CAES.
Rev. PROVIDENTIAE CAESS. Camp gate surmounted by two turrets, a star, in exergue SMK.