Willgodt Theophil Odhner was a Swedish engineer and entrepreneur, working in St. Petersburg, Russia. He was the inventor of the Odhner Arithmometer, which by the 1940s was one of the most popular type of portable mechanical calculator in the world.
According to a brochure distributed by Odhner's company at the Paris World exposition of 1900 … « Odhner had, in 1871, an opportunity to repair a Thomas calculating machine and then became convinced that it is possible to solve the problem of mechanical calculation by a simpler and more appropriate way ». It took him 19 years to perfect the design of this new machine so it could be manufactured effectively.
Machine-compteur nommée Arithmomètre
(Rechenmaschine genannt Arithmometer)
My invention is an instrument for assisting in calculating, it being adapted to add, subtract, multiply, and divide numbers without any other labor on the part of the operator than that required to set and rotate certain numbered and counting wheels, and to adjust a slide carrying a series of recording-wheels.
 US patent No 209,416
 LU patent No 32