Terminated: unknown
It’s a plain 8-digit calculator with a 9-digit LED display. The leftmost digit is used to show errors ("overflow" by displaying a small "o"), negative values and memory. Next to the four basic functions it has the percentage function, memory and an
↔
x y
key for swapping operands.
There is no battery compartment visible at the back of this calculator. Instead there is a little notch at the bottom to enable lifting the calculator out of its back cover. There you can insert or replace the three AA batteries. Contrary to what one would expect, all three batteries face the same way. Everything of this calculator seems to be designed with aesthetics in mind.
A brief manual of the calculator’s functions is printed at the back.
This variant has two sliders. One, at the right, to switch it on and off, and one at tle left to switch between floating point and two-decimal currency mode. According to this page (link validated 2025-12-06) on thimet.de there are two versions of this calculator, one without the left slider.
The workings of the M key might be a bit puzzling without the manual. Its mode of operation is however perfectly explained at the back. The M key is a kind of second-function key. The following key sequences are possible:
- M + adds the current value to the calculator’s memory.
- M − subtracts the current value to the calculator’s memory.
- M = will reveal the current value in memory without erasing it.
- M
↔x ywill swap the current value with the current memory value.
Some page excerpts from its sales brochure can be found here (link validated 2025-12-06) on calcuseum.com.
The calculator accepts Alcaline batteries but also NiCd batteries. Aristo sold their own NiCd batteries under number Aristo 6773. The NiCd batteries can be charged using the Aristo 6796 battery charger.
There is a nice page on this calculator on Das metatechnische Kabinett, a German website full of interesting technology. Read it here (link validated 2025-12-07) (in German).
According to an X-Number World article I once read (no longer linkable), the German brand Aristo only entered the calculator market in 1972 and left it due to heavy competition in 1978.