Bath Math

This calculator does not have a solar panel.
It does not have a battery.
It will work under water.
It is a bar of soap!

How this example has survived, with its original box, I do not know.
I doubt there are many of these in existence.

The keyboard and display are just printed on paper and stuck to the bar of soap.

The display reads "NE 1 4 10S" (Anyone for tennis) and
predates the current trend for "text spelling" by many years.

This set of images © Barry Smith, 2005