This coin has an unlisted workshop since RIC IX gives two separate RIC numbers based on the obverse legend breaks- 21b is VALEN-S and 21c is VALENS.
Valens
A.D. 364- 367
17x18mm 2.2gm
DN VALEN-S P F AVG; pearl-diademed, draped and cuirassed bust.
SECVRITAS REIPVBLICAE; Victory advancing left, holding wreath and palm.
In ex. CONSPΓ
RIC IX Constantinople 21b