Here's a nice little Constantine II Vota coin (vows coin) I picked up last week... Attribution: RIC 152 (RIC VII) Mint: Ticinum, ST Date: 320-321 AD Obverse: Laureate Constantine II right, CONSTANTINVS IVN NOB CAES Reverse: VOT V in wreath, DOMINORVM NOSTRORVM CAESS, ST in exergue Size: 18.8mm x 19mm Weight: 3 grams This type of coin represent vows taken by the emperor to successfully rule for a certain number of years. Sometimes they represent having just completed a number and sometimes they represent hopefully completing a term. I this case Constantine II has completed five years as Caesar under his father.
Here's a similar type of coin, but this time for Licinius. Attribution: RIC 160 (RIC VII) Mint: Siscia, ASIS* Date: 320-321 AD Obverse: Laureate Licinius I right, IMP LICINIVS AVG Reverse: VOT XX in wreath, DN LICINI AVGVSTI, ASIS* in exergue Size: 18.5mm x 19.7mm Weight: 3 grams