RE: Saito 100 Rebuild or toss buyer be ware of used engine's and planes.
Except for the buggered up plug threads, it doesn't look too bad.
The reason you have marks (wear marks ) on the bottom end of the connecting rod, is because the rear bearing is worn and allowing the rod to rub the inside of the case. A new set of bearings and a heli coil in the plug threads will have it ready to run again. (Mr. Lee is a very nice gentleman to deal with BTW )