I just got this awesome addition to my Carthage collection. It has several reasons why it is special.
1. It's Constantine as Caesar. Maxentius was trying to ally with Constantine by issuing coins for him; though he was merely awarded the title of Caesar. Maxentius also gave Constantine the last workshop, reserved for most junior. This is also the issue that Maxentius changed his title to Augustus. So this issue was actually a bit insulting to Constantine, meant to remind him he was most junior.
2. this series is tough to find...RIC says it is "rare to very rare"
3. The reverse legend for this type changes from FELIX ADVENT AVGG NN to CONSERVATOR AFRICAE SVAE
4. The fields have H ER which must stand for Hercules. The three rulers represented in this series were Maximianus, Maxentius and Constantine; who were all in the family of Hercules. None of these coins were struck for Maximinus.
Constantine I
A.D. 306-307
27mm 9.4g
FL VAL CONSTANTINVS NOB CAES; laureate head right.
CONSERVATOR AFRICAE SVAE; Africa standing facing, head left, in long drapery with elephant- skin head-dress, right holding standard, left tusk, at feet to left lion with captured bull; H-ER across fields.
In ex. Δ
RIC VI Carthage 55