I saw that too.... Just got it back from Service days ago for it's annual check. It was parked in front of my office all day. I can say for sure that nobody was messing with it here. I did have a complaint during service that the seal appeared overly squashed when closed. Service said it was normal. I believe the dark mark is an bit of Opti-Coat that I applied the day after back from service. You can see a few more going back along the edge of the roof.