Its not just a generator, but also a transformer!

Thomson Houston Co Ltd label states:
Generator (usually DC, but maybe was AC?)
1000V 100mA (100 Watt)

Transformer (Rotary)
Input: 11~12V 12A (132~144 Watt)
Output: 1000V 30mA (30 Watt)

AM label only says (and does not match)
1200V 120 Watt (100mA)

I assume the Transformer for was ship power to convert to V the W/T could use. Simple transformers use the AC wave as the working component, so I am guessing here it is using the rotating armature as the working component.
During war mechanical inverter was used, a regular DC motor driving an Alternator to create the desired AC power (usually 400Hz). Not sure if this was DC or AC.