Notes: "The Calcu-Pen is a 4-function electronic calculator housed in a large, chunky, heavy, ballpoint pen. It uses a red LED display and is powered by a single N-size battery. The Calcu-Pen was made in Japan from approximately 1975 to 1977, but the manufacturer is not known for certain. It is very possible that this was the first calculator pen from Satolex, who later produced a much slimmer LCD version. This may also have been the first calculator pen to make it to production. Two other designs were patented earlier, but there is no evidence that either was ever built. Aside from its imposing size – more than half an inch in diameter – the single most attention getting feature of the Calcu-Pen is its keyboard, made from five “quadraplane” rocker switches. Each switch can rock in 4 directions, each direction entering a different number or performing a particular function. The instructions (available for viewing here: http://www.vintagecalculators.com/html/the_calcupen.html) say to place your finger in the center of the key and push in the direction of the function you want."
