One of Kind Arithmetic Prototype Dial-A-Grade Metal Circle Education Math Chart

Description

One of a Kind Arithmetic Prototype Dial-A-Grade Metal Circle Education Math Chart
- Item for sale is as shown in Images
- Vintage 1960s prototype
- Texas inventor, Irby Lee Maples
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one of a kind rare prototype
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How it works:
circle chart outer numbers correspond to the red line on the dial arm. As dial arm is aligned to an inner number (there is a dot for correct number alignment), the outside number is the final value of the inside number multiplied by the red number it is lined up to on the dial arm. Bottom separate chart showing "100" at the left and "0" at the right is for the addition and subtraction functions. Moving the dial arm to a number to be either added from the total or subtracted from the total, allows the top outer chart number to then point to the new total.
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Example
(see photos for this example alignment)
Slider is aligned to the inner number "100" which lines up to the slider red number "3". The end of the slider is now pointed to the outer number row, showing the answer of "100" multiplied by "3" equals "300".
Condition:
Very Good condition: Shows normal signs of wear expected for age/handling
Approximate Measurements/Size:
12" tall x 11" wide x freestanding depth 3" weighing 1 LB. 6 OZ.
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