A nutating disc engine made by Charlie St. Pierre in the Greensborough, North Carolina area.  St. Pierre was an expert machinist and this fine example of machining shows it.  There is one moving part, which is the output shaft and the thick disc mounted to it on an angle.  It is an expansion engine having good expansion and several power strokes going on at the same time for smooth torque output.  The problem is one of sealing.  Everything is a point contact of the flat disc on a conical surface and there is no way to put in any kind of rings because this point changes all of the time.  I see little practical future for this design as a steam engine.