Telephone Advertising Mirrors

I saw this incredibly cool display of telephone advertising mirrors at a show - can't remember which one. Wow is all I can say. How long did it take to put this together? And how much do you love that "Secret Service" mirror from Omaha with the Strowger stick in the middle? Of course the idea is that it was secret because with the Strowger dial system - the first dial system, you didn't need an operator, thus your call was "secret." (as opposed to normal calls in those days where it was probably just assumed the operator was always listening in)