Can anyone tell me what this is?

Gm offered an adjustable speed alert that would buzz when you exceeded your preset speed.
In the late 70s I worked at a Holiday gas station in Minneapolis and we were the last stations to carry high octane premium gas.... so we saw a lot of muscle cars.. one was a 68 Camaro RS/SS 396 with 8k miles on it and it had the speed alert option. Along with just about every other option !