[thecodont]

I don’t think such a thing would work. The coin that dropped into a slot would strike a chime depending on the coin’s denomination. That audio signal went to the central office to start the phone service. The dial tone had to be present in order for the coin drop to work.

Knowing that the silver pre-1964 quarters/dimes weigh (and sound) differently than the post-1964 coins, I wonder what sort of adjustments the phone company had to make to their pay phones?

[GingisK]

Those old/new coins massed the same, and their physical dimensions were the same. A great deal of effort was put into making them that way.