The plaque, roughly 1.1 metres tall and 0.79 metres wide, carries the armorial bearings of the O'Malley family carved in shallow relief across almost its entire face. It is not the size of it that arrests attention so much as the specificity: a boar, a sailing ship, longbows charged with arrows, and a horse in full gallop as the crest. Beneath all of this, in Latin, the family motto reads "Terra marique potens", powerful on land and sea.

The slab is set within a moulded frame of four narrow limestone pieces, giving it the formal presentation of a heraldic statement rather than a simple memorial. Scholars Gillespie and Ó Comáin, writing in 2005, assessed the plaque in detail and proposed a late seventeenth-century date for its making. Their reading of the imagery is careful: the boar, a recurring motif in Gaelic heraldry, may carry echoes of Irish sovereignty mythology, while the ship speaks directly to the O'Malleys' command of the waters around Clew Bay and the western coast. The family name carved below, "O Maille", anchors the Gaelic form of the name to a monument that otherwise speaks the visual language of post-medieval European heraldry, a combination that reflects the cultural moment in which it was produced.

Clare Island Abbey is a Carmelite foundation on the island off the Mayo coast, and the chancel wall in which this plaque sits has long been associated with the O'Malley lordship. The abbey is accessible when visiting Clare Island, reached by ferry from Roonagh Quay near Louisburgh. The plaque is inside the chancel, so the quality of the light inside the roofless or partially sheltered structure will affect how legible the shallow carving appears; overcast days often bring out low-relief stonework more clearly than direct sun.