I contacted the manufacturers of pegas blades, who replied very promptly.
In short, they tell me that the notch was put in to help older eyes identify the top of the blade, but that it does not suit the hegner, and they have now stopped doing it, but some still remain in circulation with their retailers.
In short, they tell me that the notch was put in to help older eyes identify the top of the blade, but that it does not suit the hegner, and they have now stopped doing it, but some still remain in circulation with their retailers.