Measuring roughly 18 centimetres high and 13 centimetres wide, it is barely larger than a hardback book, and only about 5 centimetres of its thickness is visible where it sits embedded in the masonry. What makes it worth pausing over is what survives on its face: part of an incised equal-armed cross, sometimes called a Greek cross, where all four arms are the same length. One complete limb and portions of two others remain, the original form of the slab now lost to whatever broke or trimmed it at some point in the past.

The stone came to light during an excavation carried out in 1944 by Duignan, and was subsequently catalogued by Okasha and Forsyth in their 2001 study of early medieval inscriptions and carved stones in Ireland, where it appears as Toureen Peacaun 30. Cross-slabs of this kind, flat stones incised with a simple cross rather than the more elaborate free-standing high crosses of the same period, are associated with early Christian sites across Ireland and often served as grave markers or devotional objects. The equal-armed form is among the oldest cross types used in insular Christian art, predating the ringed or Celtic cross that became more familiar later. That this particular example survives at all, given its size and fragmentary state, is partly a matter of chance and partly the result of its being set into the wall rather than left exposed to the elements.