The fragment, measuring roughly 48 by 35 centimetres, was cut from fossiliferous limestone, the kind of stone dense with the compressed remains of ancient marine creatures, and at some point in the early seventeenth century it was pulled from its original context and repurposed as a support for a mural tomb, the wall-mounted monument erected in 1617 for Thomas Archer and Margaret Knaresborough. It stayed there, hidden underfoot, until excavations in 2015 finally brought it to light.

The slab itself belongs to the thirteenth or fourteenth century. What survives is a fragment with chamfered edges and an incised cross shaft ending in a fleur-de-lis terminal, the stylised three-petalled motif that appears frequently on medieval funerary carving across Ireland and Britain. It would originally have marked a grave, the deceased's identity now entirely lost. By 1617, whoever commissioned the Archer and Knaresborough monument either no longer recognised its earlier function or simply had no qualms about recycling it. The reuse of older stonework in later construction was common practice; what is less common is the particular layering here, one commemoration literally propped up by another, the earlier burial marker reduced to structural fill beneath a more socially prominent memorial.