I drive an Opel Corsa, and today I discovered a button under the left storage compartment:

The button is on the top edge of the storage compartment, and isn't normally seen. I checked the owner's manual and didn't see any reference to it.
Naturally, I switched it on and off, but it didn't seem to change anything.

I have a PIN keyboard installed in by car right above the button, but I don't think they're related (the button seems native to the car, and the PIN keyboard is an add-on).

What is this button?