The Aristo M66S is a handheld calculator from 1977 made by the German company Dennert & Pape AG. It measures 78.0mm x 151mm x 20.5mm and weighs 150g without batteries. The case is made of glossy and matte white plastic on the bottom with a matte black plastic front section. The display is an 8-digit blue vacuum fluorescent display (VFD) with a ninth digit that indicates negative numbers or memory usage.
Power comes from two AA batteries accessible by removing the entire back cover. There is also a socket to connect an AC adapter. The keyboard uses medium travel keys with a springy, clicky feel. Printed text identifies the functions on the white keys and country of origin on the black keys.
For its time, the M66S had typical features like the four basic math functions, percent, square, square root, reciprocal, pi, and a 5-memory register. Two-key sequences access some advanced functions like squaring a number. The display shows up to 8 digits, suppressing further input rather than overflowing. Negative numbers display a minus sign in the leftmost digit.
Inside, the M66S uses a Rockwell A5553CA chip with other ICs from ITT. High quality components like tantalum capacitors were used suggesting no expense was spared. The circuit board bends IC pins to reduce thickness. Much of the chip’s capacity goes unused, hinting at potential for more features.
In summary, the Aristo M66S demonstrates quality 1970s calculator design with its combination of functionality, slim profile, tactile feel, and attractive styling. As expected from the Aristo brand, attention to detail and robust construction are evident throughout. For collectors and enthusiasts, this model remains a fine example of vintage calculator technology.