As far as I know, yes. I'm not sure how it could be a grade without a stamp. I saw the pipe, interesting, but I have idea where he comes up with the Virgin grade.
Virgin was one of the better grades of GBD. I've never seen one unstamped. Without the stamp there is no way to identify it as a virgin unless the nomenclature is so faint it just doesn't show in the pictures. I have seen several like that. If that's the case, its value is reduced considerably.