The stone itself, a coffin-shaped slab of fossiliferous limestone measuring 1.74 metres in length and tapering from the wider western end down to a narrower eastern end, dates from the thirteenth or fourteenth century. Its surface is carved with an incised four-armed cross decorated with fleur-de-lis terminals, the arms of a cross that ends in an orb and fleur-de-lis below. But at some later point, someone decided the stone had a second use, and a new Latin inscription was cut into it in raised relief blackletter script, the angular lettering style common to late medieval stonework. That inscription records the death of James Cleere, once a burgess of Kilkenny, on the twentieth of August 1597, more than two centuries after the slab was first made.

The stone came to light during excavations at St Mary's in 2015, found at the southern end of the north transept, sealed beneath a late eighteenth-century floor level and resting over timber planks that themselves covered an oval stone-lined grave. The edges of the slab and portions of the cross are worn smooth, consistent with years of foot traffic, but the 1597 inscription is noticeably crisp and shows little of the same wear, suggesting the stone was not left exposed at floor level for long after the new text was added. The roughly dressed vertical edges of the long sides point to an original placement against a wall, though where that was is no longer known. What is known is that by the time the slab was buried and forgotten, it had already lived at least two distinct lives as a memorial. It has since been reset into the new floor of the church, directly above the spot where it was uncovered.