Suspect
There is a reason I asked the question above and it is, that in looking at this piston and it's condition. I would have to think it has been running for some time with Hi-blow-by. The wear pattern at the top of the piston, inline with the skit 90* to the wrist-pin line and the skit below that angle shows a lot of blow-by and looks as if it were running for some time in that state. The color of the blue on the skirt is the color of the die in 100LL. It would make me guess that the 100LL that blew-by the rings and onto the skirt would dry there and accumulate over the time from when the blow-by started tell this engine was shut down and you found it there. Just me guessing from a picture and no testing. Yours as always, R.E.A. III #80888