My dad was an AA superintendent and one of his jobs consisted of keeping an eye on the AA boxes in his area, making sure they were fully equipped and in good condition. They most certainly had a normal GPO phone at that period, the "button A/ button B type as already mentioned by k3k3k. Prior to around 1960, members had a "freephone facility" with an honesty box where they were requested to leave the cost of the calls. This was obviously a loss maker, and the service was finally withdrawn when it was discovered that a member had been using a box to make lengthy calls to a relative in Canada.