It depicts two kneeling figures and an angel holding up a blank shield, worked in careful relief into a circular composition. The shield's blankness is its own kind of puzzle: whoever commissioned this tomb chest either never had their arms added, or the carving was left unfinished, or the heraldry has simply worn away. What is certain is that the slab exists, or existed, and that its precise whereabouts within the graveyard are, as of the last recorded survey, unknown.

The fragment came to light in 1990 when Mary McMahon was conducting a survey of medieval churches in North Dublin on behalf of the Dublin Archaeological Society. Working at the graveyard attached to Garristown church, McMahon and Henry Wheeler found pieces of effigy tombs that had been repurposed over the centuries as ordinary grave-markers, which was not uncommon in Irish churchyards where older carved stones were pragmatically recycled. McMahon catalogued this particular piece as Slab B, a side panel from what she described as a possible chest tomb. A chest tomb, sometimes called a table tomb, is a freestanding box-shaped monument, typically with carved panels on all four sides and a flat lid, used to mark the graves of wealthy or prominent individuals in the medieval and early modern periods. The slab, broken at one end, measured 1.6 metres long by 0.64 metres wide; McMahon estimated the complete panel would have been around 2 metres in length. Her findings were published in the 1991 volume of Excavations, the annual summary of Irish archaeological work.

Garristown is a small village in north County Dublin, and the medieval church there forms part of a cluster of early ecclesiastical remains in the area. Anyone visiting the graveyard in the hope of finding Slab B should be aware that its location has not been formally established since the 1990 survey, and that the fragment may be face-down, built into a later structure, or otherwise obscured. The graveyard rewards slow and careful attention; older carved stones in Irish churchyards frequently turn up embedded in walls or serving as path edging, having lost their original context entirely. The carving itself, if visible, should show that circular reserve with its two kneeling supporters and the angel above, a small scene that once identified a family whose name and arms have since been separated from the stone that was meant to carry them.