Historic calculators invented in Nazi concentration camp will be on exhibit at Seattle Holocaust center

In an age when a smartphone or an AI voice assistant can provide the answer to nearly any math-related query, it’s fascinating to imagine using a hand-held calculator built from a collection of intricate moving parts.

Now picture that device being designed by a prisoner in a German Nazi concentration camp during World War II, with few resources and the specter of death permeating everything.

Curt Herzstark’s famed invention is the Curta calculator, a selection of which will be on display starting Sunday at the Holocaust Center for Humanity in Seattle.

Herzstark first started developing the Curta in Austria in the 1930s. His work stopped in 1938 when the Nazis ordered Herzstark’s company to help manufacture equipment for the German army.

In 1943, Herzstark was imprisoned at the Buchenwald concentration camp, where he was eventually allowed to resume design work on the Curta with the promise that it could earn him his freedom after the war. The camp was liberated by U.S. forces in 1945 and Herzstark went on to manufacture the world’s leading portable calculator until the 1970s and the arrival of electronic calculators, like the HP-35.

Don Rosen, a mechanical engineer and collector of the devices, will speak about their importance at the Holocaust center. A Seattle native whose grandfather started Alaskan Copper Works in 1913, Rosen, 87, still works at the business as an engineering manager.

“I had an interest in the Curta calculator because Curt Herzstark had a background similar to my own,” Rosen said. “He worked for his family business, and he was a mechanical engineer, and so on. And I thought to myself, ‘I want to preserve a few of these things just to have them and give them to my grandkids.'”

Here’s a YouTube video explaining how the Curta works:

Rosen said interest in the Curta spiked around January 2004 after an article in Scientific American titled “The Curious History of the First Pocket Calculator.” With the advent of eBay, people could start selling and acquiring the devices, and today Curta prices on the site average around $1,500.

Between 1948 and 1972, there were 140,000 Curta calculators manufactured, according to Rosen, and he said he bets there are about 3,000 of them left. He has 71 or so, ranging from the fourth oldest one known to exist, some of the very last ones made, and a lot in between. His are all museum quality.

“That was the fun of it, to restore them,” Rosen said. “A lot of people were curious and took them apart and couldn’t put them back together. It’s made like a watch, and it feels like a watch when you turn it.”

The device fascinates Rosen because it was all designed by one person who figured out how to miniaturize what was anywhere from 35-pound to 45-pound desktop-style calculators at the time.

“The design of the parts was done from memory in Buchanwald,” Rosen said of Herzstark. “He not only had to draw it, he had to put on the tolerances, and he had to select the materials. And he was doing that without any books or any knowledge. He had a fantastic memory.”

Don Rosen will speak about the Curta exhibit at the Holocaust Center for Humanity on Sunday, Nov. 10, from 2 p.m. to 3 p.m. The center is located at 2045 2nd Ave. in Seattle.

Learn more about Curta calculators here.