It is undecorated and uneven, measuring just 1.2 metres in length, and it marks a grave whose occupant is entirely unknown. What makes it quietly singular is its bureaucratic near-invisibility: when the scholar R.A.S. Macalister surveyed and drew the Saint's graveyard in 1916 and 1917, he included this slab in his plan but assigned it no number, leaving it to exist in the record as a shape without an identity.

Macalister's plan, published in plate XV of his 1916 to 1917 study, captures the slab lying recumbent, that is, flat on the ground rather than upright, in the eastern half of the graveyard. Its position has been precisely noted: 11.25 metres from the northern wall and 11.45 metres from the eastern wall, coordinates that give it a fixed place in space even as history has declined to give it anything else. The Saint's graveyard on Inis Cealtra is itself part of a remarkable early medieval monastic complex on the island, and a recumbent slab of this kind would typically mark a grave from the early Christian period in Ireland, when plain, unworked stones were commonly used as grave markers without inscription or ornament. That this one was drawn but left unnumbered suggests Macalister saw it, recorded its outline, and moved on, perhaps uncertain of its significance or simply running out of categories.