This device goes under different names; "dynamotor", "genemotor" or just plain "rotary converter". These were very common in military gear, and this example looks of the WW2 era. They were particularly common in aircraft and other mobile applications to provide the high tension for vacuum tube equipment from a low voltage DC supply; typically 12V(road vehicle) or 28V(aircraft) This one would be from a radio transceiver. The lower voltage output is for the receiver and audio stages while the higher voltage powers the transmitter output valve.
Rotary converters like this have also been made to produce AC output with slip rings substituted for the brushes on the output winding. These were used where the output had to be a sine wave or of high power, as vibrator or early transistor inverters give out a square wave of limited power. These days even ordinary bipolar transistors are becoming obsolete for voltage conversion, with more efficient MOSFET's taking their place.
