In the online Manuals section, we have a page with diagrams on the early style and late style vent systems. I received 6 nicely labeled color pics a while ago that are now added to the early vent style page.
It has been so long, I cannot remember who did all the hard work for me of taking the pics and labeling them all to send them in...I thank you kind Sir and please forgive my forgetfulness!
Direct link to the page:
http://www.m715zone.com/vb/view.php?pg=early_vent