Unusual Gold Cylinder

An early 19^th Century cylinder of unusual design in a gold open face case.  Keywind gilt bar movement with deep freestanding suspended going barrel, polished steel stopwork.  Plain cock with polished steel regulator, plain three arm gilt balance with blue steel spiral hairspring.  Polished steel cylinder, steel escape wheel.  Engine turned silver dial with Roman numerals, blue steel Breguet hands. Engine turned 18 carat open face case the movement hinged at 9 o'clock, reeded middle.  Wound and set through the gold dome, maker's mark "WM".