I think I may have a new clue as to what the first TOS episode in the first season was that had the Fred Steiner version of the theme tune (the "Cello Version") and what the last one with the old electric violin version was. How may I know? The trial print date theory. If the date of the trial/answer print of a certain episode was on or after the scoring of the Fred Steiner "cello" version of the theme song (given as September 20, 1966), then it's that version of the theme song that would be used on those episodes. I know "The Corbomite Maneuver" and "Balance of Terror" definitely apply to this theory, and now I think I'll add "What Are Little Girls Made Of?" to this. ~Ben