Lou,

My McCoy Stunt .19 has a lapped piston with the window type sleeve.

Picked this one about ten years ago and haven't run it yet. It has plenty of compression and seems very tight so it probably has very little running time on it.

I had a .19 and a .29 like this back in the '50's and they ran pretty well but were not quite up to the performance of the K&B greenheads.