This is the same as a Model 51C, but the absence of the C designation indicates it was produced after 1960.
See the Model 51C page for details.
Leslie Model 51
Basic Specifications
Amplifier Type
2 Channel Vacuum Tube
Output Power
See Text
Drum
1 – 15″ Speaker
Horn
1 – Compression Driver
Speeds
1 Speed (Stop/Tremolo)
Interface
6 Pin 2 Channel