ADS is the model name. Actually, I believe it was AD-S, though I have seen both A-D S and AD S in print. It was the entry level model, though as an Austro-Daimler, it was a step or two above most entry level models. The model morphed into the AD-SE in 1978 or 1979, so yours should pre-date that. The SunTour VGT sounds original, so you should be able to get a date code off the back which you can decrypt using the info on http://www.vintage-trek.com/component_dates.htm . The model year of the bicycle is usually the same or one year newer than the compoents. If I've erred, Nick will straighten me out.