At the burial ground of Killeen Cormac in County Kildare, a lichen-covered stone stands roughly a metre tall, its north-east corner marked with a series of notches and scores that constitute one of the oldest forms of writing in Ireland. Ogham is an early medieval script in which letters are represented by groups of lines or notches cut along a central stemline, typically along the edge of a stone. This particular example was not always visible; it was discovered lying face-down, pressed beneath a revetment-slab of the site's central mound, serving as structural fill before anyone thought to look at what was inscribed on it.

The burial ground at Killeen Cormac is unusual in its own right, containing no fewer than seven ogham stones in total. This stone, catalogued as the fifth of the group by the epigrapher R. A. S. Macalister in his 1945 corpus of Irish ogham inscriptions, presented him with a puzzle. He noted that the scores were very fine but cut at an unusual angle relative to the stemline, a departure from convention that complicates reading. Only two vowel notches survive with any clarity, and his partial transcription, rendered as AV[.]S[.]S[.]MAQ[.]S, leaves several characters uncertain. The word element MAQ, meaning "son of" in early Irish, appears with some confidence, suggesting the stone once commemorated a named individual in the genealogical style common to ogham monuments. The stone itself is roughly rectangular but tapers slightly toward the base, measuring around half a metre across at the top and narrowing to 37 centimetres lower down, with smoother faces to the north and south and a rougher finish on the east and west ends. After its discovery it was re-erected within the burial ground, where it remains today. More recently, the stone was included in the Ogham in 3D project run by the School of Celtic Studies at the Dublin Institute for Advanced Studies, which has produced a detailed digital record including three-dimensional imagery of the inscription.