Measuring roughly 22 centimetres high and 23 centimetres wide, the fragment is thought to be part of a larger slab of unknown original form, trimmed at some point into a neat square shape. What makes it worth a second glance is what was cut into its face: an equal-armed linear cross, the kind sometimes called a Greek cross, with a square ring framing the point where the arms meet and matching terminals at each end. The deliberate geometry of it, achieved with such economy on such a modest piece of stone, suggests a maker working within a clear and purposeful tradition.

The stone came to light during an excavation carried out in 1944 by Duignan, and was subsequently catalogued by scholars Okasha and Forsyth in 2001 as part of their study of inscribed stones from early medieval Ireland. The square-ringed cross type it displays is associated with early Christian stoneworking, a period when incised slabs rather than the later high-relief carved crosses were the more common form of devotional or commemorative monument. St Peakaun's itself is a site with early medieval associations, and the incorporation of the fragment into the church wall, whether as deliberate reuse or simply as convenient building material, means the stone has become a quiet fixture of the fabric of the building rather than a freestanding object.