The stone, possibly a voussoir or keystone, a wedge-shaped block of the kind used to form an arch, is decorated with a cross motif in a diaper pattern, a repeating diamond or lozenge design common in Romanesque stonework. It is thought to date from the eleventh or twelfth century, and its quiet removal from a boundary wall is a small but telling reminder of how medieval carved stonework often survived not in situ but as convenient building material in later centuries.

The graveyard wall from which the stone was recovered sits within an ecclesiastical complex that has been in use since at least the sixth century, when St Columb, also known as Colum Mac Cremthainn, founded a monastery at Terryglass. The site, which local tradition consistently identifies with the present church and graveyard, contains a cluster of features within what may be an original monastic enclosure: the church itself, the graveyard, a holy well, a bawn wall immediately to the east, and a linear earthwork to the north. A bawn wall is a defensive or enclosing stone wall, more often associated with later plantation-era architecture but here possibly indicating the boundary of the early monastic precinct. The monastery had sufficient standing to contribute three marks to a diocesan taxation recorded between 1302 and 1307, and by the Royal Visitation of 1615 the church still had a covered chancel. By the Civil Survey of 1654 to 1656, however, the church building had apparently fallen away entirely from official notice, with only the churchyard itself mentioned. The carved stone now held at the Hunt Museum in Limerick, catalogued as reference number 0000.0416, is the most decoratively significant fragment to have survived this long process of decline and dispersal.