Ignition switch removal 77 GMC Truck

I need to replace a worn out ignition switch in a steering column--not tilt. The wheel is off and the turn signal mechanism has been removed as well as the horn button gear. This switch does not have a screw that holds the switch in like I usually find. The column has a hole in it, I assumed for the palcement of a tool to push in on a nylon tab on the switch.

The key is in the switch and the switch rotates ok but I can seem to figure out what has to be done to get the key to release itself from the housing so it can be removed. I've tried everything I can think of and haven't hit on the lucky sequence.

Any tips would be greatly appreciated.