A souterrain is an underground stone-lined passage, typically built within or beside a ringfort as a place of refuge or storage, and whoever constructed this one at Ballyhank had no apparent qualms about repurposing inscribed standing stones as building blocks. That six such stones turned up in a single underground passage, in the south-west quadrant of one ringfort, is unusual by any measure.

The stone now under consideration is small, just 0.6 metres long and 0.3 by 0.1 metres in cross-section, and it arrived at the National Museum of Ireland broken, with the opening of its inscription already lost. Ogham is an early Irish script in which letters are represented by groups of notches and lines cut along the edge or face of a stone, and what survives of this inscription was read by the scholar R.A.S. Macalister in 1945 as ending in the formula ...]LL MAQI VORRTIGURN, meaning roughly "son of Vorrtigurn", a personal name with an intriguing British resonance. More unusual still, Macalister identified a second, older inscription on the stone, apparently scratched in "minute pin-scrapes" onto an unoccupied angle, reading DIOBI. The idea that someone once used an already-inscribed ogham stone as a surface for a quieter, secondary message adds a layered human dimension to what might otherwise seem a purely epigraphic curiosity. The stone has since been examined as part of the Ogham in 3D project run by the School of Celtic Studies at the Dublin Institute for Advanced Studies, which uses photogrammetry to capture inscriptions that are difficult or impossible to read with the naked eye.