Take your time, I put one in upside down and it leaked til I redid it. It is double lipped but you will see the right way if you check the old ones, the rusty side will have been the top.
I think there is a heavier lip and a lighter lip. the heavier one faces in to keep the oil in, and the lighter faces out as a wiper. Don't forget to loosen the vent screw when assembling.
I was thinking that. It would help other folks in the future. I'm sure since there are many references to the original post by Steptoe that a link should be put in the Tech section