These types of ringers can't be mounted on the wall because the screws that attach the housings have to be installed from the underside of the base. At first I thought that was a bit of a compromise, but the idea has grown on me.
It makes the whole setup portable, the ringer box can sit on your desk, and it's a good way to recycle 302s that have smashed-up housings.
You can also install a discrete switch underneath (without drilling holes or destroying anything) to turn off the ringer, or if you want to fiddle around with components a bit, switch in a smaller capacitor or a series resistor to turn down the volume.
Ray Kottke's reputation is so strong that he doesn't need pictures of everything he produces: his work is superb, so you can buy sight-unseen and know you're getting the best. (Here's me wondering about his prices for complete sets, and when I'll be able to afford one...)
