Some Class III stones are undressed - I believe some people label those as "Class IV"? Could it be one of those?

The cross has obviously been carved onto the stone, which does indeed seem to be a standing stone, some time after the arrival of Christianity - which would date that area to Pictish times? Watson's etymology of Kilmorich seems sensible enough, although I have seen criticism of his etymology of names in Pictish areas (notably by Dr Katherine Forsyth in "Language In Pictland", 1997). So maybe it's not a Pictish symbol stone as such, but I would be extremely surprised if the people who inscribed the stone weren't Picts. It's a pity nothing seems to be known about the chapel, I think we could gain much from knowledge of that.