The square panel, dated to the sixteenth or seventeenth century, shows a chevron between three lions in relief, a style of heraldic carving in which a V-shaped band divides the shield and flanking beasts fill the remaining space. Above the arms, the name DONOH is inscribed, leading generations of observers to connect the monument with Bishop Donough O'Brien. The problem, as scholar Talbot noted in 1976, is that the chronology simply does not hold. The plaque cannot belong to the bishop it was long thought to commemorate.

The Urban Survey of Limerick, compiled by Bradley and colleagues in 1989, records the plaque in careful detail and flags the misidentification plainly. It sits on the wall to the left of the Thomond memorial, itself a significant monument within the cathedral, and the proximity of the two has likely contributed to the confusion over the centuries. St. Mary's Cathedral is the oldest building in continuous use in Limerick city, and its interior accumulated memorials, plaques, and carved stonework across many centuries, making it easy for attributions to blur or calcify into received wisdom. Who the DONOH inscribed here actually was remains, apparently, unresolved.

St. Mary's Cathedral stands near the foot of Bridge Street in the older part of the city, and access is generally straightforward during daylight opening hours. The chancel is towards the eastern end of the building, and the plaque sits on the north side of that space, to the left of the Thomond memorial. It is not a large or obviously dramatic object, so it rewards a slow look rather than a quick scan. The Gothic lettering and the relief carving of the lions are clearest in good interior light, and the misidentification noted by Talbot makes it worth pausing over, a small carved puzzle that has been hiding in plain sight.