A Power-Mains Stabiliser.
or if you want the full title
Twin Self-Regulating Power-Mains Auto-Transformers.
I recently came across the following information in a 1947 edition of an Australian Radio Handbook. It seems to be a solution looking for a problem. It can handle an input of 190v to 300v at 150watts.
© Gary Yates Locofonic Recordings Australia
This page first written 3-4-2006 last updated 3-4-2006.