I can't figure out how the ignition coils on my 1995 E320 cabriolet are held down. When you look down at it there seem to be two register pins in two of the four corners, and what look like set screws in the other two corners. One of the two has a stripped head. Before I try to drill this thing out, how does this setup secure the coil to the head?

The only way I can figure this holds the coil in place is that the coil's hole must be threaded, but then does that mean there are threads in the head also.