Ask the seller for the make/model of the phone and what circuit board it has inside. Also ask if it has keys for the locks.
The old oak telephone booths are still out there. They have been reproduced and you can still find old originals out there. The metal/glass type full booths are called "Superman" booths.
The payphones themselves have 3 styles of casings that house everything:
Western Electric (sometimes called simply, Western or AT&T)
GTE/Palco
Hybrid
A Western Electric case is the easist to identify. Look where the coin return bucket is. A genuine Western Electric always has the coin return bucket on the left side of the coin vault door. The handset cord also comes out the front of the faceplate.
A GTE case is identified by the coin return bucket being on the right side of the coin vault door. The handset cord comes out the left side of the case.
A "hybrid" case is really a GTE case with faceplate dressup kit to make it look like a Western Electric case. The giveaway will be that the coin return bucket will be on the right side of the coin door vault.
All of the big "baby Bell" telephone companies use Western Electric cased phones exclusively. They are a little harder to work on, cramped inside, and parts are way more expensive.
Many independent Publicly owned telephone companies like GTE/Verizon use GTE cased phones.
Many competitive private payphone providers use the hybrid case. Parts are the cheapest and most plentiful for these. These cases are roomy and can accomodate a wide variety of circuit boards and add-ons inside.
I own 5 payphones all pulled in from a route several years ago. They are just taking up space as they all need updated circuit board to go back into route service again.
Here is an example of an Elcotel "Olympian 5501" in a genuine Western Electric case:
http://www.worldpayphones.com/units/unit-us-QuorTech.htmHere is a place to get payphones, parts, and accessories:
http://www.payphoneproducts.com/Here's where to get a reproduction wood booth, but you won't like the price:
http://www.payphone.com/shop/catalog/Wooden_Superman_Booth-p-16208.html