I looked but I could not find a seal I have not destroyed. I will get a pic next time I have one I will get a pic.
I think I saw two notches on the outboard side of the seal at the perimeter.
I thought they were just part of the molding process and not intended for anything. Then I saw the details on this page, near the bottom
6204-2NSE Nachi Bearing 20x47x14 Sealed C3 Japan Ball Bearings:Nachi-Bearings
"Breathing mechanism (on seal OD)".