It is the outer shell processed with brass. Quite simulation design.
Microcosm FD5 Model Dynamo for Steam Engine Model Diy Project- Generates 12V 1A
Brass Model Dynamo for Live Steam Engine
FD5 Brass Dynamo Motor Generator for Steam Engine Model DIY Projects
FD-5 Model Dynamo Live Steam Engine Model Kit Brass Dual Function Part Dynamo
Microcosm FD4 Model Dynamo Motor For Steam Engine Model DIY Project Part-Silver
FD6 Model Dynamo Working Metal Generator for Steam & IC Engine Models