The giant “prehistoric gorilla” was obviously intended to capitalize on a then-new (1933) movie called King Kong.
This head (left) was once part of a M&D mechanical model (smaller than the full-sized figure seen below) overlooking the entranceway of the exhibit’s dome-like building when “The World a Million Years Ago” attraction playing at the 1933-34 Chicago World’s Fair. This photo (left) was taken shortly after I’d acquired the head. Yes, it still works — opens and closes its mouth, rolls its eyes, etc. All you have to do is plug its cord into an electrical outlet and the head does the rest.
Page (below, left) from The World a Million Years Ago hard-back program booklet and a flier for t he show highlighting the full-size “prehistoric gorilla.”