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I am trying to identify a calculator I used in the late 60's or very early 70's. Definitely before hand-held calculators. ....Hewlett-Packard? Approximately 14" x 14" x 24" high and rolled on casters. Keypad and digital readout was on top. Add, subtract, multiply, divide only. Stack memory. RPN?

Hi Randy

Give a try to this site :

Perhaps is the calc you're looking for there...

Most of the early electronic "monsters" had 2 casters on the back side - too heavy to carry around, you just had to lift the front a bit and were able to move the calculator somewhat back on your desk. Your description limits the number of possible calculators to around 100 or so... So a little drawing (position of keyboard, display, maybe outer casing, as these were often quite "strange") might help to narrow down to a handful of possibilities.

...Hewlett-Packard? ... Add, subtract, multiply, divide only.

Definitely not HP. From this site:

The HP 9100A was Hewlett-Packard's first calculator. In the mid to late 1960's electronic four function fixed point calculators were brand new and typically cost $1000-$2500. In 1968 HP introduced the HP 9100A featuring:

* Floating point math with a range of 10^-98 to 10^99
* Log (natural and base 10)
* Antilog (natural)
* Square root
* Trigonometric (including hyperbolic) functions and inverses
* Vector addition/subtraction
* Polar/rectangular conversion
* Misc. features like 1/x, PI etc.
* A logic system that could handle complex expressions (RPN)
* Programmability
* A magnetic card reader/writer
* Options such as a printer and a plotter

Here is an image of what I remember. It didn't roll around on the desk but rolled on the floor. I apologize for the lack of details.

Edited: 8 Mar 2010, 10:54 p.m.

I haven't seen a floor-standing model yet. Are you sure it wasn't just mounted on a cabinet? The first electronic calculators (Anita, IME, Canola, Sharp) were "desktop-sized".
One exception were WANG-calculators, those used a floor-standing electronics unit and several remote displays/keyboards (which is different from your image).
All larger calculators did use a vertical display, only about 1969, a somewhat more "horizontal" (like 45o angle) type was introduced for "portable" desktop calculators.
Example:Walther ETR 1

There was a prototype Friden that was similar, but the production model was "desktop" sized (Friden 130).

See here, the black & white sketches show the cabinet size prototype.