What is my seal called?

I couldn't find a reference to it for a 7 1/4 on this site. This is where a 71 service manual would come in handy.

I know with an impact gun I could never count the revolutions of the socket correctly.

I know I was thinking that. I am "hoping" to mark the socket with white out, then tap it lightly, then wind it off slowly and count...hopefully!