yeah, they're the holes, they're in a slightly different position to cd units, but that doesn't matter.
When you buy one of those units, you do only get one key, as they can be done one at a time - basically you you push the key in one side, shift the unit diagonally so that side pops clear of its tags, then do the other side and the whole lot will slide clear.
If you pm me your address I'll post you a key, alternatively if you're anywhere near st. neots in cambridgeshire, swing by and i'll take it out for you (the stereo, that is).