The stone, which may once have served as an arch keystone, measures roughly half a metre in length, with a chamfered end on one side and a head carved in relief on the other. The face wears a mitre, the tall liturgical headdress associated with bishops, and its presence here, tumbled and half-forgotten beside a holy well, raises more questions than it answers about what once stood nearby.

The stone has attracted antiquarian attention at least since 1839, when the Ordnance Survey Letters noted a stone near Kilmoon church exhibiting a mitred head. Later, the scholar T. J. Westropp, writing between 1900 and 1902, described what may be the same piece as a carved corbel, a projecting bracket used to support a roof or arch, bearing a bishop's head. Whether it functioned as a keystone, the central locking stone of an arch, or as a corbel, its carving places it within a tradition of ecclesiastical stonework associated with the medieval church at Kilmoon, which stands roughly 157 metres to the north-east. The suboval drystone enclosure where the fragment now lies abuts a larger rectangular structure and sits at Tobermoon holy well, a site whose name preserves the Irish word for a well, tobar, alongside a reference to the moon or, more likely, a personal name or earlier place-name form.

The interior of the enclosure is overgrown and filled with loose stone, and a doorway hinge survives among the scattered fragments, suggesting the structure once had more architectural pretension than its rough drystone walls now imply. The carved head itself remains visible on the ground, a small and worn face that has somehow stayed in place while the building around it dissolved into the landscape.