Add-A-Mite Pocket Calculator

This simple mechanical pocket adder is made of aluminum with bright blue paint and dates perhaps from the 1950s. The cursor on the right is depressed and dragged to the number you wish to add, 0 to 99. When released, the cursor engages a gear tooth on the back of the disc and when you then drag the cusor clockwise back to the 0 position, your number is added to the result. Crossing from 99 to 00 causes an automatic carry into the hundreds window, allowing sums up to 2,499 (see the video below). Subtraction works similarly by starting from zero and dragging counter clockwise to the desired number.

Here is the back.

Here is a video of the adder in action (note: audio is delayed several seconds)

The knob on the left can be turned to add/subtract units of hundreds, or to reset the left window to 0.

The design is elegant and reminiscent of the much older Webb Adder but using concentric discs. The Add-A-Mite likely came 30 years too late to gain a market. I suspect that cheaper plastic dial and push button adders won out with the budget-minded grocery shopping crowd (see marketing verbiage on box and instructions below).

A 'Present' for Your Wife

"A subtle suggestion." Let's her spend what you intend!

"As acurate as a fine watch", and "Pretty as your favorite constume jewerly!"

Here is a link to an Add-A-Mite page with a photo of the disassembled mechanism: http://boelters.de/Rechenmaschinen/_Add-A-Mite/add-a-mite.html

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