Re:
I'm not sure. I wouldn't worry too much about it though, I don't think there was that much difference on earlier components. Later, the MTB stuff tended to have better/more seals, particularly on things like hubs.
My early Deore II hubs have tiny little rubber seals in the hole of the metal dust cap, whereas later Shimano hubs had a rubber dust cap/seal that extended over the spacers and lock nut.
Is it part of a road group though?
I'm not sure. I wouldn't worry too much about it though, I don't think there was that much difference on earlier components. Later, the MTB stuff tended to have better/more seals, particularly on things like hubs.
My early Deore II hubs have tiny little rubber seals in the hole of the metal dust cap, whereas later Shimano hubs had a rubber dust cap/seal that extended over the spacers and lock nut.