Shutoff valve access plate is stopping me

[kee]

What's the correct tool for accessing the shutoff valve behind this kind of access plate in this photo? the plate is unremoveable and i need to shut the water off. the condo building was completed in 1988. please help.[xx(][xx(]

[LazyPup]

It appears to have either a set screw or small access hole in the center of the cover. If it is a hole I would guess that it is a hex key mount (Allen wrench) that you reach through the hole.