Here are three very close photos of the lock.
http://imgur.com/a/VMR0AThe top photo is with the front plate spun to a horizontal position. You can see the actual keyway spans the entire width of the opening. You can see way into the back where it looks like perhaps the tip of a warded key might fit.
The center photo shows the plate at about a 45 degree angle and you can see the walls of the cylinder in the edge of the opening of the plate.
The bottom photo is of the plate in a vertical position and is similar to the 45 degree photo in that you can see the edge of the cylinder in the edge of the opening of the plate.
You can tell by looking at all three photos that the center of the lock is pretty open. Even in the 45 degree and vertical positions the warded keys I have will fit in. For this reason I think they are too small. It seems to me they would need to only enter in the horizontal position to be wide enough to engage the (wafers?). The paper tower holder key seemed wide enough but not deep enough.
I'm trying to be helpful but my terminology is probably off by a mile. I apologize for my inexperience. You folks have been more than kind and patient.
Thanks
Greg