During the period from 1978 to 1985 there were four different models of the “sorotaku”: a combination of a soroban and a dentaku, i.e. a pocket calculator. They had the model numbers EL-8148, EL-8048, EL-428 and EL-429. The instrument shown here is the battery-powered model EL-428. Its basic design is like the model EL-429, but its soroban beads are made of white plastic.
Surprisingly, the combination of soroban and pocket calculator became very popular. As the use of the soroban was so wide-spread, one would never think of using the newer but slower pocket calculator for addition and subtraction. The latter was, however, very useful if multiplication or division occurred. The combination was also very useful for showing the answer on the calculator for those that were unable to read an abacus. The model shown here was made by Sharp and its 13-place plastic soroban was suitable for business purposes.