The TES was just a logical development of what had gone before so the differences are incremental in many ways, but from memory I think it got its first big debut at the 61 Scottish. This bike (ie the 62 season TES) used the square section swingarm that had also been introduced on the MCS ('MotoCrossSpecial') scrambler for the 61 season - and is a quick identifier between earlier series round swingarm (Hawkstone/Scottish) bikes and later MCS/MDS/TES series bikes. There's a little bit of irony that an NSU Max engine in a Greeves would be legal pre60, but a square swingarm would not.