Lichtmühle, radiometer, or light-mill
Whilst at first glance this might be mistaken as some kind of perpetual motion machine it is in fact a kind of heat engine reliant on a carefully judged partial vacuum to reduce resistance and facilitate the necessary thermodynamic processes. Fascinating and mesmerising the rotation can also be used as a quantitative measure of electromagnetic radiation, most especially in the visible and infrared spectra. Mouth blown and assembled in small lamp workshops in Lauscha, Germany. Approximately 8cm diameter.