Yes, Russ that's the difference!

I suspect that the SL stand's for the humbuckers, as initially they were also produced with the tiny so called micky mouse pickups.
(I do have a T-100-D with those on)

Nigel,
Looks like the rating between 1300-1500 was pretty accurate for the 303 series.

fred
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Keyboards/Sound Units: Kurzweil 2600S, Roland VR-760, Acces Virus C, Roland G-800, Akai AX60, Minimoog, Machine Drum, Roland R8-M, mediastation x-76