You will see a lot of cancels with advertising for telephones on Irish mail.
The post and telephone were the same company up till a few years ago
here's is a article I cut and paste from wikipedia
An Post, the Irish postal administration, came into being in 1984 when, under the terms of the Postal & Telecommunications Services Act, 1983, the postal services of the Department of Posts & Telegraphs (P&T) were divided between two new organizations: An Post and Telecom Éireann (the latter being the telecommunications operator now called Eircom). At its inception, during the early years of the Irish Free State, the Department of Posts & Telegraphs was the country's largest department of state, and its employees (most of them postmen) constituted the largest sector of the civil service. Prior to this the postal service in Ireland had been under the control of the General Post Office that was established in 1660
