This is from old National stock. The choke is 31 MH and is a single section pi wound 5/8" long on a ferrite form. There are small link coils of 17uh, one at each end over the main coil. Any idea what this strange item was used for? Id say it was from the 1955-65 era. I have a large quantity if its of use to a homebrewer. Carl KM1H