The block measures just twenty-five centimetres tall and twenty wide, barely larger than a hardback book, yet its face bears an elaborately worked cross in relief set within a circle, a form associated with early medieval Irish Christian stonework and sometimes called a ringed or encircled cross. The irregularity of the block's shape suggests it was never part of a formal architectural scheme; it reads more like a devotional object, something made to mark a place or a person rather than to dress a wall.

The slab's original home was Illaunmore Island in Lough Derg, the long lake that stretches along the border of Clare, Tipperary, and Galway. Islands in Irish lakes were frequently chosen as sites for early monastic communities, offering a degree of seclusion and a natural boundary from the surrounding world. Illaunmore's position in Lough Derg places it within a landscape with deep early Christian associations, and the carved slab is a physical remnant of whatever religious activity once took place there. At some point the stone was removed from the island and eventually came to rest in the museum collection in Ennis, where it is now held as part of the county's archaeological holdings.