Well, I could not find much information about Georgia being a member of the system that shares violations from state to state (the DLC). It seems they are not. But if I were you, I'd still try to negotiate a reduction in speed in case your insurance can see the violation.

As for the Alpharetta ticket goes, I'd file a request for any evidence ALPD has relating to your traffic stop- any communication with dispatch and if possible, any in-car video/audio. If he said 81 to you and then wrote 83, there is a chance you could prove the officer wasn't even sure of the violation. That is, if he really "said" 81 and cited you for 83. Even then, if you want to get technical, you could bring up that speedometers have a ±10% margin of error for federal standards. So If you were driving at an indicated 75 or 76 mph, the speedometer's variance could have put you up to 81 or 82 mph by laser or radar. You could even bring up that on top of the mechanical variance of the speedometer, there is a variance on tire diameter (even for tires with the "same size") that could compound the reading even further. On GA400, depending on the time and traffic volume, doing 10-11mph over is not outside the average variance of drivers on there.
Also note that since there is no state-approved recalibration services. If you felt up to the job, you might even look into seeing how you could obtain logs from your GPS nav device to show what you were seeing at the time of the violation.