It's interesting stuff. The SOED defines denarius thus:
1 An ancient Roman silver coin, orig. of the value of ten asses. Also occas., an English or British penny (as the origin of the abbreviation d. in � s. d. etc.). LME.
2 A unit of weight equal to that of a Roman silver denarius. LME.
3 More fully golden denarius. An ancient Roman gold coin worth 25 silver denarii. M17.