The Romans did not appreciate the idea of selling the leadership of the Roman Empire to the highest bidder, preferring for it to go to a man who had military distinction and service; right away there were three more men proclaimed as emperor by their troops: Pescennius Niger, Clodius Albinus and Septimius Severus. Severus marched on Rome and the praetorians left Julianus to his fate, which was beheading.
Obverse: bust right, [IMP.CAES.M.DID.SEVER.IVLIAN.AVG.] Reverse: Concordia standing left, holding two standards, [CONCORD.MILIT. S.C.], 28mm and weighs 20.5 grams
Listed in Harold Mattingly's Roman Imperial Coinage as Number 14, and an identical piece from the same dies was sold by vcoins.com four years ago for $901.
This coin came from Arcadian Fluck who dealt in coins from the late 1950s up until his death in 1990; he enjoyed working with ancient coins, even though much of his inventory was very low grade material; most of his coins he acquired from various mail order coin dealers in the 1960s.
See scans 5357 748-91