Edwin Thacher, a civil engineer, invented this device in 1881. It is a mechanical cylindrical slide rule designed for rapid and accurate calculations, particularly for engineers and architects. The inner cylinder slides and rotates freely inside the outer cage-like cylinder. The measurements and scales are more accurate than standard slide rules, and the metal construction protects it from moisture and temperature changes. Marvin Lee Calhoon owned this collector's item and sometimes used it for work. He was an electrical engineer in the railway, maritime, and aerospace industries in Seattle and the Pacific Northwest from the 1940s through the 1950s.