Unique monaural Membrane Stethoskop and its original box made in Germany, c. 1920. The stethoscope has a membrane that screws onto both changeable chest pieces, as well as on the ear piece. The membranes are made of a clear plastic material (although they look black in the image). There is an anti-chill rubber ring that fits onto the rim of the chest piece as shown in the chest piece on the left. There is no makers mark on the stethoscope, and this stethoscope may have been made specially for an individual physician.

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The use of a membrane on monaural stethoscopes was distinctly unusual, although an early twentieth century Aesculap catalogue shows a metal monaural with a membrane cap that could be placed on or taken off the chest piece.