The basic coins were the as and the sesterius.
In the eastern part of the empire an other system was in use, with oboles (copper), drachms (silver) and talents (gold).
A Roman soldier in the 1st c AD earned annually 225 denarii of which 100 was subtracted because of the costs of subsistence.
)* in Republican time 2,5 as equaled 1 sestertius. That 2,5 ratio can be written as I+I+S (S from Semi =1/2) which reads as HS