???? (Cleaned up version -- you know that's not what I typed first...)
View attachment 262478
Doesn't look like a thrown chain (without a chain guard). All I can think is someone took the chain guard off at some point and... put it back wrong? Then... fixed it later... but did nothing to try to clean up the scarring? There's some minor wear on the chrome, but that would likely be because steel's a lot harder than aluminum. Going to try to smooth out the back edge of the crank case a bit. Doesn't really show unless you're looking at the chain guard close, but it's still not right.