Grade Three planet

Grade 3 planets were primitive worlds which were in a pre-space age state. The Central Galactic Census Bureau defined a grade 3 planet as "a planet that has no significant technology, no knowledge of other worlds, and as such, has a protected status". Strellin was considered grade 3. (AUDIO: Order of the Daleks)

Ribos was also considered grade 3, and would take thousands of years to reach grade 2 status. Until then, commercial mining could not take place as the inhabitants were unaware of other life forms. (TV: The Ribos Operation)