The Calcu-Pen is a vintage piece of electronics from the 1970s that doubled as a calculator and pen.

Here’s some historical information from the Vintage Calculators Web Museum:

The Calcu-pen is a very unique calculator from the 1975 to 1977 time-frame.  One of the earliest ads from 1975 shows the Phenix International company of Wayne, New Jersey (USA) selling the Calcu-pen for $79.95.  Ads in Scientific American from early 1977 show the price as low as $19.95.  The actual manufacturer is not known and is not present on any of the currently-known printed materials for the calculator (such as sales ads and operating manual).  The back cover of the operating manual has a guarantee with returns to be sent to Tru-phonic Sound company of Bellwood, Illinois (USA), but that may have just been one US distributor or servicing agent.  An LCD version of a Calcu-pen (with the same spelling) was made in 1981 by Satolex, an Asian company. There may be a connection.

The calculator is made out of metal and constructed very well.  It is shaped much like a cigar tube, 6.3 inches long and about 0.6 inches in diameter.  The five keys on the barrel are termed “Quadraplane” rocker switches in the Phenix ad.  Each switch will rock in four directions, allowing four numbers or functions per key.  The display is an eight-digit red LED.  The Calcu-pen is powered by a single “N” sized replaceable battery.  The on/off function is controlled by rotating the end cap of the pen – opposite the pen end.  The pen itself is a small ballpoint which moves into position by rotating the pen nib end.  When rotated up into the barrel, the pen tip is completely protected.

How to use the Calcu-Pen

A PDF of the manual included with the pen can be found here.

On/Off

To turn the pen on, you can twist the pen cap with one click. Another twist will turn it off.

Computing with the Pen

Once the pen is on, you can use the 5 rocker buttons to compute mathematics.

Each button is a 4-way rocker that can be pressed on different sides to select different numbers and operations. The operations on the calculator include addition (+), subtraction (-), multiplication (x), and division (÷). Additionally, the largest number you can type out or compute is 99,999,999 as the pen is limited to 8 digit spaces.

It’s quite a beautiful piece of retro technology and although it’s not the most friendly interface to compute with, as the saying goes in mathematics: Please Excuse My Dear Aunt… Calcu-Pen 😀