Originally Posted by
himespau
the plugs from the junction boxes I knew were always more quarter sized. Never had the guts to try getting a gumball with one, but I often wanted to try.
They grew close to quarter-sized when wiring got larger. On the really old junction boxes for single-conductor knob-and-tube wiring, they were close to penny sized.
Two-conductor wire was bigger, and needed bigger knock-outs, about nickel sized.
Then they grew again, to accommodate three-conductor cable in a bushing to prevent chafing.