Here is a fairly rare type that depicts Constantine II holding a horse. This coin is not in RIC VII, but should come after RIC VII Trier 326. There is an example in Die römische Münzserie Beata Tranquillitas in der Prägestätte Trier 321-323 by Zschucke from the second workshop-- RMBT 13a. This coin may have had some tooling, as the arm position looks odd and the fields seem to show evidence of smoothing. This makes it hard to be sure about the bust, as RIC and RMBT have cuirassed only, but this example seems to show some drapery. The shield also has an elaborate scene. RMBT lists 42 different types of shield decorations from Trier and this one is #40. It is described as Constantine I with a soldier nearby, being approached by Constantine II, in a position of deference, with an attendant/ soldier. Constantine II A.D. 321 19x20mm 3.9g CONSTANTINVS IVN NOB C; laureate, draped and cuirassed bust left, decorated shield on left arm, holding horse by bridle with right hand. BEATA TRAN- QVILLITAS globe set on altar inscribed VO/TIS/XX; above, three stars. in ex. PTR RIC VII Trier –; RMBT 13a
The obverse legend seems also tooled but maybe it's just to enhance what was already there (the horse and shield) rather than invent it.
Another horse and fairly fancy shield that I just got...excuse the scratches, it is in a slab. Constantine II A.D. 323 CONSTANTINVS IVN N C; laureate and cuirassed bust left, decorated shield on left arm, spear over shoulder, holding horse by bridle with right hand. BEATA TRAN- QVILLITAS globe set on altar inscribed VO/TIS/XX; above, three stars. in ex. •PTR crescent RIC VII Trier 415 The shield is decorated with two people, maybe Constantine I and Constantine II, shaking hands.