What gives it away, or rather what used to give it away before a rear extension swallowed the evidence, is a sandstone window tucked into the north wall at first-floor level: a two-light opening measuring roughly 1.4 metres by 0.85 metres, fitted with a hood-moulding above it and a reveal almost a quarter of a metre deep, with glazing-bar holes still visible in the soffit. These are the fingerprints of late medieval or early post-medieval construction, the kind of careful stonework associated with buildings of some status from the sixteenth or early seventeenth century.

The window itself is a two-light type, meaning it was originally divided vertically by a central mullion, a slender upright of stone, though that mullion is now missing. Hood-mouldings, the projecting drip-strips carved above window openings to throw rainwater clear of the frame, were a common feature of quality construction in this period and help establish the building's age alongside the overall proportions. There are further clues elsewhere on the structure: a fragment of a cornice survives on the north-east angle of the east gable, suggesting the decorative stonework once continued horizontally around that face of the building. Below it, a corbel, a bracket of stone projecting from the wall, indicates that an adjoining structure once stood on that side, now long gone. The western half of the building has been modernised internally, with partition walls inserted at various points, though the early fabric survives elsewhere in sufficient quantity to confirm the sixteenth or early seventeenth-century date.

The most consequential change to the building came after it was inspected in 1993. A rear extension was subsequently added, incorporating the late sixteenth to seventeenth-century window into its interior and effectively removing it from external view. The window that had survived on the back wall of a busy town-centre building for perhaps four hundred years is now enclosed within a later addition, invisible from the street. The rendered exterior of numbers 57 and 58 O'Connell Street gives no hint of any of this to a passer-by.