1975 · Slide Rule Maker's Calculator · Work 947 of 1,871
The dividing workshop of a slide rule factory in Hamburg, on a workbench a stack of slide rule blanks, long bars of smooth white plastic, entirely blank from end to end, on top a narrow pocket calculator fifteen centimetres tall with a black front and cream-white side edges, near its top three small white slide switches, a dark red window with a soft red glow, below twenty square keys in five rows, two red, several orange, the rest cream-white, every key plain smooth and unmarked, a cable to a small black plug-in power unit, a hand in a grey work coat sleeve laying it down, a grey idle dividing machine behind, fluorescent light.
What it was used for
The M 75 is a pocket calculator from Aristo-Werke Dennert & Pape of Hamburg, a firm that had lived off the slide rule since 1872. It was built for technical calculations: white and black plastic case, trigonometric functions, logarithms and memory functions, 15 x 6.1 x 2 cm with its cover, run from 3 AA cells, rechargeables or a mains unit, with instructions in 8 languages. It was sold by the same firm whose main product it made redundant. Slide rule sales collapsed as cheap calculators spread; according to the Heinz Nixdorf MuseumsForum, Aristo ended slide rule production in 1978 and calculator production in early 1979.
What was new
According to the Heinz Nixdorf MuseumsForum, Aristo bought the rights in April 1972 to a design by Hilmar Bentert for Luther-Elektronik in Berlin, launched the M 27 from it in autumn 1972 at 466 DM, used a General Instruments processor in its self-developed M 64 of autumn 1973, and sourced a desktop model from Japan in 1978. Rechnerlexikon states that Aristo's calculators did not succeed on the world market and that production ended in 1979 under Hans Dennert. The barb: the company did not outlive the device with which it meant to replace its own product.
What the sources leave open: The dating of the M 75 is open. Heimatmuseum Hoerste gives 1974, the Deutsches Kunststoff Museum 1975 to 1985; no company source for 1975 was found. The figures on the M 27, M 64 and the end of production come from the Heinz Nixdorf MuseumsForum blog and from Rechnerlexikon, not from a company archive.