It's an A-D S, probably '76-'78. The A-D S was Austro-Daimler's entry level at the time, using their (Puch's) own hi-ten tubing. It would've come stock with that Tourney GS rear derailleur as well as a Shimano crank and Weinmann center-pull brakes. The frame looks bad, but I don't see anything that goes beyond the surface. The chrome on the fork crown will likely be pitted after you clean it up, but the rest of it can probably be media blasted and rattle-canned back to life. If you want to go a step further you can have Greg Softley make some decals for you. The chain's trashed so I'd pop the $15 for a new one. Whether it's worth fixing all depends on what you want to put into it and what you want to get out of it. It's never going to be worth a lot in terms of resale value, but if it's something you enjoy fixing up and riding around when it's finished, well, welcome to the club.