The ogham text, incised along the left-hand angle of a slab two metres long, was pressed against the earth, serving as a roofing lintel inside an underground passage while the message it carried sat in total darkness beneath it.

Ogham is an early medieval Irish script in which letters are represented by groups of notches and strokes cut along the edge of a stone, typically read upwards from the base. The inscription on this particular stone reads CROCCAN MAQI DOMONIGART, a formula meaning roughly "Croccan, son of Domhnagort", the kind of memorial or territorial marker that appears on ogham stones across Munster and beyond. The stone came to light in 1981 when quarrying at Coomlogane, in north Cork near Millstreet, accidentally broke open a souterrain, an underground stone-built passage or chamber associated with early medieval ringforts, often used for storage or refuge. The souterrain sat within a ringfort, and when archaeologists excavated the site, they found that two ogham stones had been repurposed as lintels in the second chamber of the passage. Whether this was done with any awareness of the inscriptions is impossible to say, but the effect was to seal the text away entirely. Both stones were removed to Millstreet Community School, where this one remains. The companion stone was later transferred to Millstreet Museum, where it is now on permanent display.

The stone at Millstreet Community School is not a museum object in the conventional sense, which gives it a slightly different character. Visitors with an interest in ogham may find the companion stone at Millstreet Museum the more accessible of the two, but knowing that this slab spent centuries as anonymous building material, its inscription invisible beneath a chamber roof, adds something to reading those notched letters now.