I've been using Aquarian American Vintage heads for about 7 years. The Thin and Medium weight heads are both 1 ply as are Remo Diplomats and Ambassadors. The coating that is used on the Am. Vintage heads is thicker and thus heavier than other modern style coatings. So a "medium" American Vintage head ends up being more of a Medium-Heavy (though still 1 ply). The idea is to replicate the sound of the calf heads that originally came on the drums. The coating usually wears fairly quickly and after about a dozen hours of playing time, you're left with a smoother (more calf-like) surface that is a bit thinner than it was out of the box yet still very responsive to brushes. I have a 5.5"X14 snare and I personally prefer the Medium weight for the batter side, as I have found the Thin weight to be less durable. I do use the Thin wieght heads on the snare side though. If you are lucky enough to have a 4"X14" pregressive jazz/Max Roach model, I would probably use Thin heads top and bottom. Hope this helps!

-Chris