It is an achievement of arms, meaning the full heraldic display, not merely a shield but the complete arrangement of helmet, crest, supporters, mantling, and motto, all compressed into a frame less than three quarters of a metre square. That anyone thought to fix such an elaborate piece of aristocratic self-presentation to the façade of a building intended for the poor is, in itself, quietly telling.

The carving is executed in false relief, a technique in which the background is cut away to give the impression of depth without the figures fully projecting from the surface. The shield is divided into four quarters, combining the arms of Butler of Dunboyne, featuring a chief indented charged with three escallop shells in the first and fourth quarters, with the three covered cups associated with the wider Butler family in the second, and a fess, a broad horizontal band, representing the le Petit family of Meath in the third. Above the shield, a defaced helmet, meaning one whose surface detail has been worn or deliberately removed, carries a crest of a demi-falcon with wings displayed, rising from a plume of ostrich feathers, while the mantling, the decorative cloth-like flourishes that frame the helmet on either side, sweeps outward in lobed curves. A lion gardant stands on the right-hand side and a horse on the left as supporters, and the motto scroll beneath reads TIMOR DOMINI FONS VITAE, the fear of the Lord is the fountain of life. A later inscription in capitals along the lower part of the frame reads "James Donboyne", added at some point after the original carving was complete, suggesting the plaque was either claimed or commemorated by a subsequent hand.