The stone had been inscribed in ogham, an early medieval script used across Ireland and parts of Britain, in which letters are represented by notches and strokes cut along a central line. By 1854, it was gone, broken up beside a holy well and either thrown into the fill or pressed into service as building rubble. What survives is not the stone itself but a rough sketch made fourteen years after its destruction.

The site in question is St Marnock's Well, recorded alongside St Marnock's church in the area known as Burrow. According to Caoimhín Ó Danachair, writing in 1958, the ogham stone was broken up there in 1854. The circumstances are not entirely clear, and the sources use cautious language throughout, with words like "alleged" and "supposedly" doing considerable work. What is more certain is that in 1868, a Church of Ireland clergyman named Reverend J. Shearman made a rough sketch of the inscription before the stone's destruction was complete or fully forgotten. That sketch is now the only record of what the stone looked like. It was later catalogued by R. A. S. Macalister, the scholar who spent much of the early twentieth century systematically documenting Ireland's ogham stones, and appears as number 18 in his 1945 corpus.

The well itself, designated in the Sites and Monuments Record as DU015-007002, sits beside the remains of St Marnock's church in the Portmarnock area, the place-name itself preserving the saint's memory. Visitors curious about the site will find the church and well rather than any surviving ogham inscription; there is nothing to read in stone here, only an absence to account for. The value of coming, if you do, is partly in that absence, in understanding how much early medieval material was quietly lost, repurposed, or mishandled well into the nineteenth century, often without anyone thinking to record what was being destroyed until it was nearly too late.