Leo I. AD 457-474. Æ Nummus, Lion . ByzantineEmpire, NGC Certified.Leo I, also known as "the Thracian", was Eastern Roman emperor from 457 to 474. He was a native of Dacia Aureliana near historic Thrace. He is sometimes surnamed with the epithet "the Great", probably to distinguish him from his young grandson and co-augustus Leo II.