I picked up an Automatic Electric three weeks ago for $75 at a swap meet. The few things I know about old rotary payphones:
Depending on your service provider, the rotary phone may or may not work without modifications (real insightful, huh?
). The point is it may work as is so try it. At the very least, you should be able to receive incoming calls as is. Usually if you are wiring this up you would hook the red wire to the ring terminal and the green to the tip terminal.
If you are looking at a phone in person such as at a swap meet or a garage sale (as opposed to eBay), you can usually tell if the phone works by touching the wires to a nine volt battery. You should at a minimum be able to here a clicking noise as you touch the wires to the battery.
There are usually two locks on most pay phones. The upper lock will allow access to the actual phone electronics and the lower lock will allow access to the coin box. Drilling out the lock on most of these older payphones does absolutely nothing but destroy the tumblers. Even with the center of the lock gone, you probably still can not open the phone up. Fortunately, the upper part of the phone is usually a standard key and available for about $10 -$20. The key for the coin box is unique. Many times you will find a phone with coin box door missing or without a lock due to this reason.
Good luck on finding a phone you like.