I see the wrinkle too, and I am pondering what could have caused it, as the rest around it seems 'virgin'. I can't think of an accident in evolving something from the side or rear that gives this type of damage, and have no other damage to show in the wheelhouse (although we can only see the bottom inch, it still looks untouched) , neither is the rest of the wheel well compromised. In the corner near the diff mount there is also some rough area, but it looks to be just a crappy caulk job from Karmann (was too in my car in places)
Could something from under the car be picked up by the wheel and be pulled up into the wheel well, getting jammed in between the wheel and the bottom of the floor?
Could something from under the car be picked up by the wheel and be pulled up into the wheel well, getting jammed in between the wheel and the bottom of the floor?