The object in question is an ogham stone, a type of monument inscribed with an early medieval script in which letters are represented by notches and strokes cut along a central stem line, most often used to record personal names and lineage. What makes this particular stone unusual is not just its inscription but the long, piecemeal manner in which it came to be understood.

The first fragments surfaced in 1845, but it was not until around 1930, when another piece came to light, that the scholar R. A. S. Macalister was able to reconstruct enough of the text to read the inscription as: SEDAN MAQQI CATTABGBOTT AVVI DERCMASOC. The stone itself, measuring roughly 1.18 metres by 0.3 metres by 0.2 metres, records a lineage reaching back to Derc Masoc, who in the mythological history of early Ireland was a son of Cathair Mór, a figure said to have been among the first kings to rule the whole island. Derc Masoc was held to be the ancestor of the Uí Deirc Mosaig, the dynastic family associated with Ath Cliath Cualann, the early name for the Dublin area. The inscription, then, links a scrap of Wexford shoreline to the legendary origins of a ruling family whose territory lay far to the north. The story of the stone's recovery was not finished there: archaeological excavation in 1987 uncovered the final missing fragment, completing a puzzle that had taken over a century to assemble. The reassembled stone is now held in the National Museum of Ireland.