It is a GIANT bicycle re-badged for Schwinn. It is a decent basic bicycle with SUNTOUR derailleurs front and rear. Beyond the closure of Chicago factory, Schwinn increasingly turned to importing much more. Schwinn's contracts with GIANT propelled GIANT into a major player in the bicycle industry such that they soon overtook Schwinn in both status and importance.
Your GIANT built Schwinn is not quite as simple as say a VARSITY-CONTINENTAL-SUBURBAN-COLLEGIATE-SUPER SPORT that has the one-piece forged steel ASHTABULA crank which any 11 year old kid can service with a large Crescent wrench and a large Flathead screwdriver.
Your "GIANT" is a fine bicycle and it will be about the same as servicing most any Japanese or Taiwanese bicycle from the late seventies through the mid eighties.
It is a good basic bicycle. It might have less perceived prestige than say a RALEIGH or a PEUGEOT but at least as good as their compareable offerings of that time, if not better. You will find that it will be a nice rider that will serve you well. Don't listen to those that say that it isn't high-line enough to bother with. Yes, perhaps if your only aim is to build a really super-light racing bicycle, but otherwise don't worry because that WORLD SPORT (GIANT) will easily keep up with the B - group Riding Group even if you have never ridden and are the weakest rider among that B-group. Once serviced, and fitted with new cables, tires, tubes, brake pads and grease, that World Sport will be durable enough that you will not need for any service work other than brake pads, tire tubes & tires for probably three to four years, this assumes that you ride 1000 miles per year. Basic bicycles might not have the lightest weight components but the rugged durability is an acceptable trade-off for the typical bicycle rider. Now if you're wanting to be like Lance, such a basic bicycle is like comparing a stock 2020 Honda Accord to the 2020 HONDA powered Indy 500 Race Winner. You can make basic upgrades easily if you wish, given that there is a lot of stuff that has been refined in the past forty years than can easily interchange & swap with your existing equipment. Just don't attempt to make a competitive racer out of it. Just because there are people that race old PINTOS and old Corollas on dirt tracks, and even sometimes in drag racing too, does not mean that those are the best choice for a racing platform, given the multitude of better choices that were developed later..
Last edited by Vintage Schwinn; 08-29-20 at 12:51 PM.