RIC doesn’t list any siliqua with this mintmark for Theodosius I, but it is listed for other rulers—Valens, Gratian and Valentinian II. It was probably struck circa 383, which was close to his quinquennale and around the last time this mintmark was used.
Theodosius I
A.D. 379- 383
AR Siliqua
17mm 1.9g
D N THEODOSIVS P F AVG; pearl diademed, draped and cuirassed bust right.
VOT V MVLT X surrounded by laurel wreath.
In ex. T Chi-Rho E
RIC IX Thessalonica --
