The 1929 World Almanac and Book of Facts. Facsimile Edition. American Heritage Press, Workman Publishing Co., Inc., 1971.
Claire A. Gilson (1889-1962) was trained as a civil engineer and developed the circular slide rule, patenting it on October 19, 1915. The same year he founded the Gilson Slide Rule Company in Niles, Michigan. In 1919, he bought the Richardson Rule Works. In 1922, Gilson patented a mechanical calculating device. The firm moved to Stuart, Florida in 1927. The original symbol for the business was the “Be Wise” owl. The company's rulers were often marketed under other names such as Lietz, Post, and Dietzgen. In 1962, with declining health, Gilson sold the business to a friend. Unfortunately, he passed away before he could fully instruct the new owner in the intricacies of manufacturing slide rules. The new owner persevered and got the company up and running again, only to face unassailable competition from the new generation of electronic calculators. The company ceased operation around 1975.