Magnific Nero  Sestertius or medallion

As in undocumented as a sestertius in my catalog of Van meter, and the experts of the forums do not achieve a decision, I have not clear if this is a medallion made in the XVI century (I got from a medallion of a jewel of that century) or a real sestertius.

Some experts say is not possible that sestertius exist and think is a form of medallion, other experts say that all match with know sestertius, although i was unable to locate.

Patina was reparated in some tiny places and a wax layer was add to protect from the weather 

Bought in the 2000 year in an auction of ancient jewelry on Roma, Italy.