Welcome to the "Tribe" as we like to call ourseves!
The "S" models started with the Silvio 1.0, hence the "S". There was a 1.5, 2.0, etc., until the name drop/change to S30/40. The Silvio 2.0 series had a 27 degree seat angle. The S30 a 33 degree seat angle (I believe) and the S 40, well, a...