Rear wheel bearing seals

[voucht]

Hi,
I just cleaned some parts from the donor by electrolyse, it is very efficient, almost “magic”.
I removed the seals and bearing from the rear wheel hub carrier. RH and LH parts are exactly the same.

IMG_2536_1.JPG

But one of them has an odd seal. It is mostly done of a metal ring, instead of being all rubber with metal ring inside as the other ones.

IMG_2537_1.JPG

Can anyone tell me if this is normal, or what is the reason why one of the 4 seals is different from the 3 others?

Thank you by advance for your help.