The inscriptions read "IMPMARSILBANNACVSAVG" on the obverse and "VICTORIAAVG" on the reverse (Image courtesy of Dirty Old Coins, LLC).
In their inscriptions, ancient Romans habitually used the letter "V" to denote both a "U" and a "V". Therefore, these inscriptions augment as "IMP(erator) MAR(cus?) SILBANNACUS AUG(ustus)" and "VICTORIA AUG(gusta)".
The obverse, in English, means Emperor Mark(?) Silbannacus Divine (the latter an attribution of divinity that Roman emperors took upon themselves, in imitation of Egyptian Pharaos.)
The reverse, in English, means Divine Victory, implying that some military victory had been obtained through divine providence, and invoked as his justification for calling himself Divine (Augustus). All Roman emperors called themselves Augustus, by the way.
One of the authentic coins was found in Rome, the other one in a Northern province, giving rise to the belief that Silbannacus might have been a Gaul, particularly because of the name's "acus" ending. What is clear about all this is that Silbannacus is undocumented and, therefore, largely a mystery.