The Probert Encyclopaedia of Money

SOLIDUS

The solidus was a gold coin struck by Constantine in place of the aureus, and known later as the bezant or byzant. Adopted by the Franks it was in use until the time of Pepin. The silver solidus was reckoned to equal twelve denarii, or silver pennies, and was thus equal to a shilling. The abbreviation S for solidus was adopted in the initials LSD (pounds, shilling and pence) in British pre-decimal coinage.
Research Solidus