Correct. it was the high RPM version of the O.S. 21 sized engines. It used the same case for the airplane, car, boat engines. it had different bearings, timing setup of a tuned pipe. I need to put a drive washer, spinner and prop nut on it.
Thank you for looking, I do appreciate the effort in helping.
The old O.S. .12SE engine had a crank that looked like this one.
http://www3.towerhobbies.com/cgi-bin...?&I=LXBJRH&P=7
In looking, I did found a Super Tigre .28 engine with a threaded crank, it looks like this one.
http://www3.towerhobbies.com/cgi-bin...?&I=LXZUH4&P=0
Buzz.