Today (Dec 10, 2004) I received the above photo, which was taken in 1990 at the Smithsonian Inst. in Washington, D.C. It is another Atkinson Cycle engine, but must be a very early model. There was some question in my mind if it had the Crankshaft/Piston Rod 'monkey motion' to complete all 4 strokes with one revolution of the flywheels, but if you look real closely, I think you can see the intermediate rod hanging down toward the back. Also, note that it has TWO flywheels, unlike any other photos of it that I have seen.
The lay shaft looks like it has a worm drive at each end, but this cannot be so on the crankshaft; A worm wheel on the crank could never drive a worm. Also, if they are worm gears then it makes interesting reduction calculations.

Just a wild guess by a friend of mine, but he thinks this may be the Utilite engine that Atknson brought out in 1891. See Cummins 'Internal Fire' page 223. This engine is certainly more modern in concept than the originals, yet still retains the hot tube ignition from the earlier model.

If anyone has further knowledge about these early Atkinson engines, please let me know.