A solidus from the time of Constantine the Great
The billon (roughly 25% percent silver) coin was the first appearance of VLPP type. Circa 313 A.D., Trier.
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Sources for the study of the Byzantine Empire: Imperial Byzantine Coins in the British Museum
Catalogue of the Imperial Byzantine Coins in the British Museum By Warwick William Wroth , British Museum Dept . of Coins and Medals Published 1908. --> Catalog of Imperial Byzantine Coins in the British Museum - Vol I by