To all you people who thought it was a valve seat.... how in the **** can it get in the oil pan without a hole in the m'fn piston...
Valve lock seemed possible, but they dont look missing in the pic.
So what about a piece of pin boss, or how about a ruler next to the debris so we can give a more educated guess here...it could very well be the bottom of the locks...they do look deep in the retainer