I wouldn't press that if I were you....

Some folks would install a generic aluminum momentary starter button in the dash on CIS cars, and hook it up to the cold start valve to help the car start when the accumulator and or fuel pump check valve were tired and didn't hold fuel pressure overnight anymore.
Holding it in while cranking the starter would help a cold motor with low initial fuel pressure start in the morning.
Guess that ones already been figured out though...

I just pulled my car out of storage to see if i had one of those. Its -4 degrees in Chicago and I have been looking for hours. Can you take some pictures to help me find it.

On my car it's in the position of the fog lamps. But my button is more like a headlights switch.

Some high-school Harry probably aded this as a fake nitrous oxide button to impress his friends -- didn't realize they were already impressed by his ride (unless it was some Beverly Hills Jr.-jock) :p

Even though we have an answer I just had to say ...
 

Even though we know it's the antenna defeat I just had to guess that it's the on/off switch for your camera's autofocus.

That was good!!! LOL

Was the previous owner into computers? It sounds like the "Turbo" button on my first PC.

I have the same hole in my dash but no button. Pisses me off that there is a hole in the dash. But I do have an electric antena so I guess it all makes sense now. Of course there is no radio anymore. Total Conumdrum!