Most R1s have suggested age ratings by the anime company - used to be the case that almost all just said "Unrated" on VHS and early DVD.
Just picking 2 off my desk randomly, Inu Yasha from Viz says "Not Rated. Parental guidance suggested" and has a little Viz design of "T for Teen". World of Narue says "Not rated." and has a "Suggested 13 Up". They just suggest ratings to cover themselves, but they're not consistent or externally checked unless they go through the formal movie rating system.
R