Attended pay stations were staffed offices where customers could make phone calls and then pay for the calls placed. Since the earliest pay phones had no coin slots, payment would be made to the attendant. Although it is not completely understood why tokens were used at attended pay stations, it is assumed that tokens facilitated payment in some manner. Telephone tokens were also produced for deposit directly into the pay phone. Security has always been a concern for any public device that requires the user to deposit money.
Pay telephones are no exception.
People have used anything from lower valued foreign currency to metal washers to cheat the machine. To combat those trying to cheat, security tokens have been used in telephones. The basic concept is that the pay phone had a coin slot, or some special device attached to the coin slot, which accepted only those tokens with the matching groove, punch or slot design. Thus, neither foreign currency, blank metal planchets nor washers would work. Only the appropriate security tokens could be used.