This article describes a custom creation, custom theme, or other fan material, made by a Brickipedia contributor. It has never been, is not, and will not be officially released.
I've seen some of these floating around, but most of 'em are just edited photos of the current motors.
So, I think I'll take a crack at it too!
S stands for 'Small', in this case. It might get mixed up with the Servo Motor...
The entire motor would be on a 2 x 4 base, and be about 5 plates high.
(Pictures coming soon, need to draw them out first!)