ROMAN REPUBLIC AE as. Semuncial standard, 'Lex Papiria' series, Rome, 91 BC. Laureate head of Janus. Reverse - Prow right; L•P•D•A•P. (Lege Papiria de assis pondere) above, no I mark of value in right field. Crawford 338/1 (10 specimens), Sydenham 678. 27mm, 12.2g.
The weight, and the unusual abbreviation above the prow, show that this coin was struck on a new weight standard of half an ounce instead of an ounce, as authorized by the Lex Papiria of 91 BC. The semiuncial standard caused havoc in commerce, despite the new law, and the semuncial standard was rejected just a few years later at the outbreak of the Social War in 88 BC