Useful for winding small air-core coils, i.e inductors for projects such as audio crossover networks or other L-C based filter networks.
Brand new but old 1970's stock from PMG (then became Telecom and now Telstra)
Marked on the former:
PWM 68 No 12
3 tinned terminals embedded into the former for both the coil and external connections
Former internally measures 12mm high x 16mm diameter (estimated) winding area inside the former
Externally the former measures 16mm height x 23mm diameter