might be an error coin where instead P (
PERP = perpetuatae - meaning "long -lived") an T cutted and few or hundred coins minetd before noticed... anyhow seems unlisted to me if not Barbarian imitation - which I belive it is not..
From otherhand TERP anyhow makes no sence; TR.P. or TR.POT I can understand - Tribunicia Potestas, but with TERP bite me as have no ideas!