 Philatelists refer to the configuration as '"perf 15 x imperf", or in the USA as "perf 15 horizontal", because the stamp is perforated 15 gauge (holes per 2 cm) on the horizontal and imperforate on the vertical edges.Because of the shared design it appears identical to the first 2d value definitive stamp issued on 6 December 1922 with the "Map of Ireland" except for the imperforate vertical edges.It uses the first Irish watermark that was a stylised design of the two overlapping letters 's' and 'e' making an 'se' watermark representing the name of the country "Saorstát Éireann" (Irish Free State).