Aes Formatum Lambskin; curved troughs; toothed peaks

Aes formatum — raw cast bronze in shaped forms — preceded the introduction of aes signatum and eventually struck coinage in central Italy. These curved-trough, toothed-peak pieces were not coins in any functional sense but served as weighed bronze currency in a pre-denominational economy where value was reckoned by the libra. The "lambskin" designation refers to the undulating profile of the cast surface, a morphological classification used by modern scholars rather than any ancient term.