Denison stethoscope with its box made by the J. Ellwood Lee Co., c.1890. In 1885, Charles Denison came out with an entirely new stethoscope model. The earpieces were made of hard rubber which led into woven tubes and a large chest piece. It came with three interchangeable chest pieces for hearing different types of sounds. The tension between the earpieces was accomplished by a screw mechanism. Denison's model was widely accepted. So widely, that many makers began marketing inferior pieces of the "Denison Stethoscope." Denison became outraged at the poor quality of stethoscope being manufactured with his name. He wrote a critical article in which he stated precisely how his stethoscope was to be made, condemned the makers of poor instruments, and praised only one American company, George Tiemann & C0., for their quality craftsmanship.