Hammond module from I believe an L-100, L-103 or similar subvariant of spinet organ - vibrato amplifier. I think these use an LDR and can be modified or adapted in a number of ways, published online, for different audio and sonic purposes!

Brand: Hammond
Type: Vibrato Amplifier
Instrument: Organs
MPN: H-AO-47-1
Country/Region of Manufacture: United States