If you recall where you saw that phrase, provide more context, and an accurate article can be written on that specific mislabeled file’s origin. Otherwise, treat it as a broken search fossil — a “Trex” of the hypno-hentai world.

There is no verifiable, mainstream media known as "Saimin Seishidou Trex" with a standard Episode 16 that falls within a "6 cen 20" (possibly meaning "6th century 20th? Or a price/rating of 6 cents out of 20?").