I recently won this coded coin with the workshop in the left field. I already had an example with workshop in right field and in exergue.
http://www.constantinethegreatcoins.com/CONSERVATOR/Diocletian
A.D. 289- 290
Ӕ Antoninianus
25mm 4.5g
IMP C C VAL DIOCLETIANVS P F AVG; radiate and cuirassed bust right.
CONSERVATOR AVGG; Diocletian stg. r., and Jupiter stg. l., sacrificing at altar, each holding sceptre; Γ in left field.
In ex. XXI•BI•
RIC V Siscia 263
