Eric,
I'd thought the SunTour VX derailleurs were mostly from the late 70s or early 80s, and the Sugino AT from the mid 80s or later. But I'm just guessing, kinda.
The Sugino AT, by the way, is a great triple crankset. I've heard some folks rate it up there with the TAs. I've got one on my too-new-for-this-list RB-2, and I love it. (For a while I had a Sugino Super Mighty, a Campagnolo copy, on there, but the hills in this part of WI convinced me to go with a triple.)
Nath Dresser
Spring Green, WI