Another Doraville cache but, oh no! A Mystery Cache! OK, lots of folks avoid puzzles but they can be really straightforward, like this one! So if you're a beginning cacher, trust me...try this out and you'll get a quick smiley. You vets should have this one done in a snap.
So you're going to go to the posted coordinates. You'll find yourself at Doraville City Hall and there's no need to go into the building. What you want is info from a plaque on the entry porch, the plaque telling you about when this building came to be. It was planned and financed from 19AB to C9DE.
You will subtract the number AB from the posted latitude and you will add the number CDE (ignore that pesky, superfluous "9") to the posted longitude. That will get you final coords not too far away. Go get your smiley!