This bust type, D1- helmeted, draped and cuirassed, is not recorded in RIC. It should come before RIC 134. Bastien records one example (#81).
Crispus
A.D. 321
20x20mm
CRISPVS NOB CAES- helmeted, draped and cuirassed.
BEATA TRANQVILLITAS- globe set on altar inscribed VO/TIS / XX; above, three stars
In ex. PLG, C|R in fields
RIC VII –