Novus 650 Mathbox Calculator National Semiconductor Corp.  with original box

tested using a power supply vey clean, all leds function properly.  from years of non use the keys take a few presses to operate, everything does work-see pics.

Distinctive features: Very basic calculator (only 6-digit display and does not have a decimal point key), with silicon chip mounted directly on circuit board.

Technical details:
Display is 6 digits, red LED.

4-function, fixed decimal point (2 decimal places, useful for simple money calculations), with calculations entered using RPN (Reverse Polish Notation, similar to mechanical adding machines) - note the 'ENT+' key and no '=' key.

Main integrated circuit - under blob of resin.

9v (PP3).

69 x 126 x 24 mm. (2.75" x 5.0" x 0.95").

The Novus 650 was announced in late 1974 with a price tag of US$19.95

An earlier version of this calculator is known with two integrated circuits in standard dual-inline packages.

This calculator shows the minimalist approach in order to cut down on the manufacturing cost. Note how few electronic components it uses -

• The display is only 6 digits.
• The integrated circuit is not in a conventional package - it is bonded to the circuit board and protected by a blob of resin.
• It has a fixed decimal point - set at two places of decimals, which is useful when calculating money values - so no "." key is needed.
• It uses RPN (Reverse Polish Notation) calculation entry, so the integrated circuit needs less memory electronics and a "=" key is not needed.

National Semiconductor was a 'vertically integrated' calculator manufacturer, like Texas Instrument and Rockwell in that it was semiconductor company which produced calculators using its own integrated circuits and LED displays.  This meant that the electronics components could be developed to its own requirements, could be supplied at a lower cost, and if there were any shortage then it would supply its own manufacturing first.