As already mentioned 29A keys were used by the Regional Bell companies.
There are about 100-different key combinations since each Bell company often used several different combinations within their territory, often divided into separate parts of the states and large cities they served.
Thus, 29A L-27, was used by Pacific Telephone to serve Northern California while another list number was used for Southern Cal. Their Nevada Bell subsidiary used yet another list number key.
NyTel’s New York City had several list numbers assigned to the various boroughs as well as others that were used throughout the rest of the state.
29B keys had thousands of different combinations and corresponding list numbers since they were furnished to many different CoCots rather than telcos.
In the instance of the pay telephone in the eBay auction, it may be a crap-shoot as to whether you can find the right key on the first try if the number card with the area code and prefix is missing. Otherwise it should be rather easy to order the proper key.
Something does appear to be rather hokey since they state these phones were acquired at a government auction. How did a government body acquire and auction telephones belonging to a telephone company? And why would a government body remove the instructions cards, especially since most public employees would not know how to remove them. Someone must have had access to the coin box keys to remove the vault doors. It is also strange that they did not remove the upper-housing locks before they auctioned them.
Just my 2-cents worth!