It is the kind of object that could easily be overlooked in a storage context, yet the carving on its surface connects it to a tradition of early Christian stone-working that was already ancient when most of Ireland's great medieval buildings were still unbuilt.

The slab originally came from Inchcleraun Island, a small island in Lough Ree on the Longford side of the lake, which was the site of an early monastic settlement associated with Saint Diarmait. Cross-slabs of this type, upright stones incised with a cross and used to mark graves or define sacred ground, are among the more common survivals of early Irish monasticism, but this one has a detail that sets it apart from the plainer examples. The roughly subrectangular slab, round-topped and cut from a limestone that still carries the faint impressions of ancient marine fossils within the stone itself, bears a Latin cross with expanded triangular terminals at each arm. In the lower left quadrant, almost as an afterthought, a small incised spiral, described as a double or s-shaped motif, has been worked into the surface. That combination of the formal cross and the curvilinear ornament is characteristic of the early medieval period in Ireland, when abstract decorative traditions that pre-date Christianity continued to find their way onto ecclesiastical objects and stones.