Ook Leslie 301 werd exclusief voor Thomas ontworpen en deze box had veel weg van de 350, want deze was ook voorzien van 4 buizen eindversterkers, samen goed voor 65 Watt. De 350 was in principe voor een Conn bedoeld.

Hier nog wat Engelse informatie:

There are 3 channels: Pedal (1 speaker), Main Channel (2 speakers) and Rotary Channel (1 speaker) - 2 speed.
There are not enough lower louvers for the rotating component to be a Rotosonic - at least like all the ones I have seen so far.
Maybe it's more like those small Leslie modules with 8" speakers that were built into some organs? 
I assume the main channel speakers were mounted against the side louvers. 
Leslie used that 4-channel tube amp for other models that were only 3 channels as well (like the 610) - usually two of the little amp boards were wired together in those cases. The brochure also says "144 watt peak power amplifier" - which would make each amp module 36 watts.
That sounds way too high if this did use the standard 4-channel tube amp as per the web link above (the little amp modules in those were something like 13-16 watts each)
Unless of course using the "peak power" measurement was the usual marketing "ploy"

Amplifier Type 4 Channel Vacuum Tube
Output Power 65 Watts total
Drum Unknown
Horn Unknown
Speeds Unknown
Interface Custom

En hier slechts TWEE louvres onder!