Richter's scale of cultures was a method of describing cultural achievement.
Prior to learning their true nature in 2267, Federation experts rated the Organians at approximately class D minus on this scale; presumably, this corresponded to an agrarian culture with hand- or animal-powered machinery. (TOS: "Errand of Mercy")
According to a PADD created for Star Trek: Insurrection but not readably seen, the Evora (then apparently known as Bartisi) ranked B Minus on the Richter scale (sic).  In the movie, they were said to have been significantly less advanced then the Federation, and having only achieved warp drive a year before.