I'm fixing up the final drives in one of my D6 9U's and have noticed a difference in the seals. They are of the same type (springs) but one is overall thicker than the other. The thinner one is on the right in the picture and has six pins on it instead of three. They both have "CAT" on them. I'm going to glue new cork seals on them. I'm guessing the thicker, three pinned style is a later production. Am I correct? Any info would be appreciated. Thanks.