Hitherto unpublished and unknown documents from the Archivio di Stato, Florence, concerning the earliest work of Jacopo di Cione. This lost work consisted of a large vault mural painted in 1366 in the Guild House of the Judges and Notaries in Florence. Information concerning painting materials (blue pigments and gilded tin) is provided with evidence for an early beginning with Jacopo's long-time collaboration with Niccolo di Pietro Gerini. -- AATA