A vintage (1930s I think) Actina transformer or resistance (sorry I'm not sure!) which would have been for a cine projector.
It says "For use with 500 Watt / 110 Volt lamp only".
Completely untested - as found - has one lead coming from it with a 2-pin plug (see pictures).
Looks to have been well used, but in reasonably good condition. Internal workings looks okay - shown in pictures.
SOLD AS SEEN - UNTESTED - STRICTLY NO RETURNS.