That last post is actually the perfect segway into my post.
The earlier ones didn't have any seal around the pierce pin. I've never had a problem with them leaking but I don't believe anyone even Nelson has any more if that one breaks (which I have only heard of happening once) This will lead to one possible compatibility issue.
Since there was no seal, and no collar for a seal, the frames didn't have a hole big enough to accommodate a seal going through them. Check yours, this may require some trading out or modifying of the frame.