That certainly does look like a tab for mounting a fender or similar object. My opinion though, it looks like the tab at the bottom rear of the fender where the bracing strut would attach. That doesn't show up well in the comparison photo. I'm wondering, given the width of the fender to cover the airwheel tire, were there two stuts supporting the rear of the fender, one to either side? Or, was it like a bicycle fender with a long u-shaped brace which rivets to the fender in the middle? Given how wide these fenders were I would think two separate struts is probably more likely. If that is the case it looks like it could be a rear mounting tab to me. LTM -John