Stirling Engine
Tax included.
Yes, a working Stirling Engine. From the Heebie Jeebies range. Engineers and scientists will approve. Powered by heat differential - so use an object much hotter or much colder than the ambient air temperature and it will drive the piston, and keep the engine chugging away apparently forever (but actually until the 2 temperatures get too close together), So, a cup of hot tea or coffee, or an ice bucket, will drive this engine for you. Elegantly made , sturdily constructed, 18cm H, a fascinating engineering wonder, a rare and special gift.