It actually appears to be an old 'Princess' phone, which wasn't designed to hang on a wall. The receiver wouldn't stay in the cradle, mounted on the wall. A Velcro strap would have been a better solution.
Sorry to be a stick-in-the-mud, but I guess I just didn't see this as humorous.
Well Ralph, now that we sticks-in-the-mud have totally hijacked this thread...
The Trimline was a different phone from the Princess, in that it was wall-mountable, as well as having the dial in the handset. The Princess was designed to be used in a bedroom, so was not wall-mountable. It also had the dial in the base. Both phones originally pre-dated the modern RJ11 "modular" plugs and jacks (as pictured in your post).