Bright yellow and industrial in design, the Odhner Model 239 is a post-war evolution of the classic pinwheel calculator. By the 1950s, these machines were found on desks from Stockholm to New York, where clerks cranked away to balance books or calculate payroll. Sleek, reliable, and built like a tank, it represents the peak of mechanical calculator design — just before electronics swept them away.

This is a later Comptometer, from the 1950s. Notice the array of colorful keys, each representing a number. To use it, trained operators would press multiple keys at once, creating an incredibly fast workflow. In fact, skilled Comptometer clerks could outpace early electric calculators! Offices employed entire teams of these “human engines,” their fingers flying across the keys to keep up with the pace of modern business.

The Felix pinwheel calculator is a Soviet workhorse. Produced well into the 1970s, long after the West had moved to electronics, these machines cranked out sums across factories, schools, and government offices. Modeled on the Odhner design, the Felix became a symbol of practicality: rugged, simple, and nearly indestructible. For many Russians, this brown, heavy machine was the calculator of daily life — proof that sometimes old technology lingers far longer than expected.

This unusual device wasn’t for accounting or trade — it was for science. The Marbel Blood Cell Calculator helped laboratory technicians count and classify blood cells. Each key represented a different cell type, and pressing it tallied the results on a row of counters. In an era before digital lab equipment, this tool made medical work more accurate and reliable. It’s a reminder that calculators weren’t only for money, but also for medicine.

Here we have the Perkins Brailler, designed by David Abraham. It’s not a calculator at all, but a writing machine — for the blind. Each of its six main keys corresponds to a dot in the Braille system. By pressing combinations, users could emboss letters onto thick paper. Compact, durable, and revolutionary, it gave independence to thousands of blind students and professionals. Many Braille writers still trace their roots back to this iconic design.

This earlier Felix pinwheel model, made in 1935, shows the rugged beginnings of Soviet calculator manufacturing. Heavy, iron-bodied, and mechanically faithful to Odhner’s original design, it was built to last. At a time when rapid industrialization demanded accurate accounting, machines like this were essential. They stand as relics of a world in transition — bridging the gap between 19th-century mechanical ingenuity and the digital revolution that was still decades away.

By the late 1960s, the Swedish company Facit was a leader in office technology. The C1-13 combined sleek Scandinavian design with rugged mechanical power. Clerks would punch in numbers on the keyboard, then crank the handle to watch results appear instantly in the display windows. Fast, quiet, and reliable, it became a global export — right before electronic calculators began their rise and made such mechanical marvels obsolete almost overnight.

Here’s a pocket calculator — before electricity. The Addiator was a slim metal plate with tiny columns of numbers. Using a stylus, you slid the notches to perform additions or subtractions. No batteries, no gears, no noise. It fit neatly into its leather sleeve and was popular with engineers, accountants, and even schoolchildren. Imagine pulling this out of your pocket in the 1940s and impressing friends by “magically” crunching numbers with nothing but a pen-like tool and some clever design.

Here’s another version of the Facit C1-13, highlighting its compact, modern look. Compared to bulky pinwheel machines, this design was more ergonomic, easier to use, and fit seamlessly into 1960s office life. For a brief moment, it seemed like the future of calculating — until Japan’s electronic revolution swept through, ending the mechanical calculator era within just a few years.

This striking German calculator, with its colorful keys and brass finish, looks almost playful — but it was all business. Made by Rheinmetall, better known for typewriters and weapons, this “special edition” model was a precision tool for accountants and engineers in the interwar years. Its rainbow of numbers made complex input easier, while its sturdy construction reflected Germany’s reputation for mechanical excellence.

This is the Suan Pan, the Chinese abacus. At first glance, it’s just beads sliding on wooden rods. But for over 700 years, this was the laptop of merchants, bankers, and scholars. With a quick flick of the fingers, people could add, subtract, multiply, and divide faster than many early clerks using pen and paper. Even today, in some parts of Asia, the abacus is still taught — not as a relic, but as a way to sharpen mental calculation skills. It is, quite literally, the oldest continuously used calculating tool in the world.