Could this be from a loose wrist pin? They are clamped to the rod, but might be loose in the piston? Crazing on the bearing surface could be from heat? It is not something I have seen often so I don't know for sure. Hotrod Lincoln has a good tip for cleaning any small scratches. We used to call the sand paper he is talking about "Crocus"Cloth. It came on a roll and had different grits and widths as I recall.
