Digicus (Abacus + Digital Calculator)
These hybrid calculators are not a joke. They were produced in Japan for only a few years at the time when digital calculators were first gaining acceptance.
After many centuries of using the reliable soroban (Japanese abacus), many Japanese were skeptical when the newfangled calculators were introduced. They did not fully trust the calculator and would use the abacus to check their results! Also the Japanese are very fast using an abacus (every young student was trained extensively in using the soroban -- many still are!), and often preferred to use the soroban for addition and subtraction while using the calculator for multiplication, division and square roots (which are time consuming on a soroban).
The elegant digicus captures a heady moment in human technological progress -- the transition from counting with sticks and beads to transistors and liquid crystals. Not only the Chinese, but even the Romans relied on the mighty abacus, and thousands of years passed before something better finally came along! How long will our trusty digital calculator last?
As far as I know, there were only four models of digicus ever made for the Japanese market, all by Sharp. These are the EL-8148, EL-8048, EL-428, and the EL-429 (shown top to bottom, above), produced from 1978 to 1985.
The EL-8148 is my favorite. It has a wooden soroban frame and all wooden beads and posts. The calculator fits into the frame and can be removed. It has 19 columns of beads! Extra columns are desirable on an abacus when doing complex calculations. Intermediate results can be calculated on the left before they are incorporated on the right.
The later models use plastic frames and beads.
Here are a pair of seemingly identical units, one is the EL-428 and the other is the EL-428S
I can't see any difference between them, though the stamped text on the back differs slightly.
Interestingly, the styling of the solar model EL-429 (shown below) is pleasingly reminiscent of the El-8148.
The digicus (my term) is sometimes referred to as a sorocal (soroban + calculator) or sorokaru or sorotaku (soroban + dentaku, which means calculator in Japanese).
This link includes a link to translate this into English (courtesy of Google).
Here is a link to a Korean model:
(I would love to add one of these to my collection, please send me a note if you know about one)
And another link to the History of Computing site: