This is the engine I chose to begin my career as an amateur machinist. 
It's a Rudy Kouhoupt design for a two cylinder, double acting marine
engine.  I chose it purposely because, at the time, it was way beyond my
abilities.  I guessed, quite correctly, that I would learn a lot while
trying to build it.

The engine actually took fifteen years to complete.  Work intervened,
including two long stays abroad but the major problem was that, every
time I returned to the engine, I would look at some of the parts I made
and say, "What junk!  I can do better than that now" and proceed to
remake the offending parts.  I didn't keep count but some of the parts
in this engine may have been remade as often as six times.

Near the end, I was beginning to lose interest and, to spark my
enthusiasm, built a much simpler oscillator engine.  Thus the oscillator
was the first engine I completed but this engine, completed next, was
technically my first engine.

To this day, whenever I see it in the display case or run it at a show,
I get a little rush of self-satisfaction.