I remember them as well, although a distant memory now.
I can remember Deggeller Magic Midway carrying one box on the back of a Sky Wheel trailer, it didn't fold up, but was just racked back there.
Bit off topic, but I remember the wooden boxes for electrical used on midways back then as well.
As a kid loved to play "carnival" in the backyard with what I had. One item I had was a wooden box with a lid about the same size and I would run hoses and stuff into trying to mimic a midway