It seems a bit unlikely that they recorded, mixed, pressed and released the album in just one month (if that were the case they would be superheroes), so it is more likely that it was released in January 1971, or at most, in February.
In this case the correct date should be 1969, this because "Beat 69"'s catalogue number is E 351, so "Supreme Psychedelic Underground" should have been released soon after "Beat 69" in 1969