Mine has screws in the retainer. I had pulled the screws, and removed the cover.
Under that is another "layer" - it's pressed steel, it has a flange that runs around the edges just like the cover (the 4 screws go through it) - and there's a seal pressed into that.
Never saw something like that before - I had started prying that out but when I got to the point of mangling it, that's when I stopped. I figured if I've never seen one before, they can't be too easy to find.
I'll go back to prying on the axle, but won't be able to till tomorrow.
thanks for all the advice.