At the head of the cross, a socket cut across the stone once held an upright slab in place, a kind of tenon-and-mortice arrangement in old ecclesiastical stonework. That secondary slab is gone, and with it whatever inscription or decoration it may once have carried.

The flat slab beneath was recorded by the scholar R.A.S. Macalister in 1916 and 1917, who dated it as ninth-century in character and described the cross design as worked in cavo rilievo, a technique in which the background is cut away to leave the design standing in shallow false relief rather than being carved as a raised form. Macalister also recorded the testimony of a man named Delany, who recalled seeing the missing upright slab still standing in its socket. Delany remembered it as roughly a foot high, but could not say whether it bore any lettering or ornament. That uncertainty has remained ever since. The island itself, Inis Cealtra, carries one of the more remarkable concentrations of early medieval Christian remains in the west of Ireland, and this small slab, easy to walk past, sits quietly within that wider complex.