Hey Jim, is it just me or does this forum stink or what???? NEVER get any reply on here for any question I have. And the questions are not dificult at all!!!!. Did you ever get any help with the tank?? I bought a Mark 20 last month to replace my old one I had when I was a kid. Found it locally and in great shape, couldn't pass it up. I was thumbing through my manual and it had some stuff on the tank. 2 types are available. 1 has a button to presure the tank and the other uses a lever. I remember reading your post awhile back when first posted. I fiqured it'd be answered by now. Guess not!!!! If you need info, I could scan what I have and send it to you.
http://www.aomci.org/askamember/index.html is a much better forum. They will answer you!!!