I have a front wheel with a Dura Ace hub in the 7400 series days. It has the plastic dust or bearing covers on the sides with the 'open' and 'close' markings. What's the scoop on these. I can rotate it to the 'open' position but I can't get the cover off. I assume if I can get it off I can get to the bearings to add some grease.
I have those hubs, too. The "Open" position opens a little hole to add more grease w/o taking the dust covers off. I don't think I've ever actually done that with mine as I typically do a complete overhaul and replace the balls which requires taking the axle out. With the axle out, the dust covers can be pryed out with a screw driver, but there's usually not a need to take them out.