36 g
Hazelnut.
I will try to explain and motivate my opinion. When I/you look carefully at the photo where the corroded edge of "arm 36 g" and the bolt is shown it is rather obvious that there was no movement between these. Any such movement would have been stretching of the arm and would have lead to scratching and deformation of the "lock" substance still surrounding the six-edged bolt head. My very personal opinion is that what we can see from the picture is a corrosion damage to the arm. Possibly induced by the tension caused by the bolt. I have seen very similar corrosion phenomena on some older outboard engines.