The artifact is part of a private collection; it's 3 cm long, and it's dated 3rd century AD.
In ancient Rome, magic gems were used as protective amulets and harbingers of good fortune.
The obverse of this gem depicts the cock-headed Anguipes in armor. The reverse shows a mummiform figure with a snake encircling its body.
The inscriptions, a mixture of Latin, Greek and other languages on both sides are typical of magic gems, in that only a few can be recognized as words with semantic meaning (such as seµesea on the front, meaning “eternal sun”). The inscriptions are so called voces mysticae, invocations and secret names, which would only be understood by the spirits themselves who are being invoked.
I was going to say... but some of that looks Greek...