This coin (if exists) could be probably in national Archaeological Museum of Florence (MAF).
"In 1895 the entire Uffizi Grand-ducal medal collection was transferred to rooms in the new national Archaeological Museum of Florence (MAF) - Polo Museale della toscana. [...] Since 2007, work has been taking place on the reorganization, inventorying and publication of the numismatic material in the MAF coin cabinet. It comprises coins of the Greek world (more than 6,000), Roman Republican coinage (about 4,000, up to Augustus), Roman Imperial (more than 20,000 items, from Augustus to Romulus Augustulus) and Roman Byzantine (about 800 pieces)".
Coins are successively published. The last volume of which I am aware of is "Sylloge Nummorum Romanorum - Italia - Firenze XIII, Diocletianus - Licinius II".
Constantine is not present, so maybe in XIV volume the enigma of this little coin will be solved.