Duumvir (II VIR)

One of two Roman officers or magistrates united in the same public functions (one of two members of a duumvirate). The title duumvir, written as II VIR, appears on provincial and colonial coinage when duumvir was the title of the highest officials of the city. In imperial times, the second duumvir of the city was often the emperor.

Dictionary of Roman Coins

Please add updates or make corrections to the NumisWiki text version as appropriate.
DUUMVIRI, so called from their number (two), were magistrates inferior in rank to the Pretors, and who presided as judges at a court (curia) in Rome, where cognizance was taken only of criminial cases.  The office was held in much consideration during the Republic, as well for the power it conferred, as on account of its antiquity, the creation of the duumviri being referred to a peiod so far back as the reign of Tullus Hostillius. 

View whole page from the Dictionary Of Roman Coins