The inscription is in Greek, and the characters may have thrown you a bit.
Reverse reads PERI - N(TH)ON
For what I see of it the obverse reads ....IANOS SEBACE = SEBASE which is the name and the imperial title.
Ben is probably right about the parallel with TRAIANOS but the figure on your coin appears to be radiate, while the headgear on his obverse figure seems to be more tight fitting. That could be radiate too, I guess.