Muldivo Mentor

Serial No. 181499

Date: 1950s

Capacity: 10x8x16

Price paid (including postage): £17.30

This is a German machine, a Model WSR160, manufactured by Walther – who also made James Bond’s PPK automatic pistol. As might be expected from a company in the firearms trade the engineering of this machine is first class.

It has all of the usual refinements of a high-end machine (also present in the Schubert DRV).  However, it is clearly a better machine than the Schubert.  Another feature of this machine is that dividends can be entered directly into the accumulator via knurled thumbwheels attached to the number wheels.  This potentially saves the time which would otherwise be spent in setting up the dividend in the normal way – by entering it into the input register and turning the crank once to transfer it to the accumulator, then clearing the “1” from the counter register.

Another refinement is that the carriage moves from left to right against spring pressure.  This means that when performing a division calculation the movement of the carriage from right to left is aided by the spring.  It also means that following a multiplication calculation, the carriage can be returned to its original position by pressing a button.  Another control under the right hand end of the carriage determines whether zeroing the accumulator returns the carriage to its home position.  This control is absent on later machines.  See the user guide for details.

Yet another interesting feature of this machine is that the pinwheel setting levers do not rotate with the rotor.

Muldivo was the British importer and seller of Walther machines.  In Britain the mid to late 1960s, there was a scheme to introduce calculators into schools, and many manufacturers offered discounts to educational authorities.  In 1966, the Muldivo Mentor was offered to schools at a special discount price of £49 10/-, which included a manufacturer’s educational discount and a Board of Trade remission of import duty.

This particular machine is in full working order. The plastic caps for the number setting levers, and the lever for overriding the counter direction, tend to go missing.  The fact that I have two of these machines with their full complement of caps is thanks to the two other machines sans plastic caps which reside in the “parts bin”.


Muldivo Mentor (Later Version)

Serial No. 206283

Date: 1960s

Capacity: 10x8x16

Price paid (including postage): £20

This machine came off the production line approximately 25,000 machines later than the other machine.  It lacks the carriage control lever of the other machine, and has a different badge, but is otherwise little different.

If I had to choose a manual mechanical calculator for use on a daily basis, the Muldivo Mentor would be hard to beat.  There would only be a need to use a different machine if there was a technical requirement for more digits.


Walther WSR-160

Serial No. 155141

Date: 1950s/60s

Capacity: 10x8x15

Cost (including postage): £40

This is the Walther badged version of the Muldivo Mentor.

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