Cylindrical white ceramic or Bakelite coil form with five metal connector pins on one end and a removable black plastic or Bakelite cap on the other. The body features a series of small perforations running in a straight line along one side. The cap fits snugly over one end, designed to secure internal wiring or components.
This component was used in radio tuning circuits as a precision coil form, designed to fit into Hammarlund’s variable capacitor and radio assembly systems.