Just received my first used engine in the mail today. I have always been a little leary, but figured I would give it a shot and see what happens. I purchased an OS 55AX for $99 shipped. As per the ad, engine was like mint condition, slightly used with only about 8 flights ( give or take 20 im sure). Anyhow, first thing I did was take the engine apart. It appears to be in very good shape. Everyhting is nice and smooth. For you engine experts, Im sure its normal, but was wondering what/ if anything the piston would be able to tell you about the initial runs? SEE PIC.
If there is anything specific we should be looking for when inspecting a used engine, please fill us in.

Im gonna try and make sure to run the engine this weekend. Compression is strong. Wondering if I should run it per the manual as if I was breaking it in, or is it too late for all that and just run it normal?