Are you testing us or asking?
At any rate, it's the universal drop key to open a sliding elevator door from the outside without the car being there.
The elevator door that it opens will have a circular hole in the elevator lobby side, you feed the key in, the pivoting part falls down and then you can turn it to catch a lever and release the elevator door interlock. Voila, the door opens!
Some brands have more specialized keys, with fobby things at the end of the pivoting part, like GAL and Otis, and there are also crescent-shaped ones (instead of round).
So what's the prize?!!? (I've already got a key, so a P1D would be nice...)
cheers
daloosh