Yes, it is a deadman switch. A switch is also piece of false hair, like a pony tail, that can be removed - 1950's language and before. What a great pun!! The people who first knew wringer washers would have also called a false ponytail "a switch".
The flat little bulb "switch" would have been...
We just bought a Maytag Wringer (N2LPS) at a local auction. White round tub with turquiose knobs. Great shape, no chips in tub, turns on, pump works. I bought the Maytag because my worthless Calypso felts wool instead of spinning water out like normal washers. Dangerous to wool sweaters...