My repro bumper definitely has that semi-circle. In fact, I assumed it was defect associated with the repro! I'm relieved to hear it's actually a "feature".
As for the overriders, there is a subtle but noticeable difference between originals and repros. However, unless you've seen them next to each other, I think it would be hard to tell if an overrider is original or repro just from a description.
Keith