This book tells the story of a family-run company that can be regarded as a classic example of a medium-sized "hidden champion". The use of Mahr calipers in workshops and factories had already begun as early as 150 years ago during Germany's industrial expansion. Gottingen's Mahr corporate group - with locations on several continents - had long been exporting high-precision measuring devices all over the world. The company's products themselves are less conspicuous, yet, thanks to their excellent performance, impact the industry's optimization processes and thus the everyday life of the people. As a stellar example, Mahr stands for precise measurement in the millimeter to nanometer range, from the workbench to the clean room, from the courageous founder to the innovative high-tech enterprise.It all began with Carl Mahr's business that first came onto the scene in 1861. He supplied precision mechanics, forestry offices, factories and railway companies with measuring devices. His son, Oscar Mahr, then opened the door to interchangeable production with the aid of go/no go gauges that enabled mass production as we know it today - also advanced by the armaments industry, as is carefully traced in this book. Members of the Mahr family led the company through the post-war period and economic miracles, through busts and booms, into the present, making up what is now the fifth generation. This portrayal, rich in illustrations, is based on extensive and sound research. Here, 150 years of engineering and economic history are interwoven with a profound and exciting portrait of entrepreneurial and inventive spirit.