While precise dating remains challenging for many of the castle's buildings, excavations revealed multiple floor levels in this particular structure, measuring roughly 10.5m by 9m. The earliest level featured a fine sand floor with gullies, ash spreads, a kiln and a water-retention pit, while later levels included cobbled surfaces and a central raised masonry feature resembling a workbench. Large posts were eventually installed inside the southwest wall, likely to support the roof, with ash and oxidised clay present throughout - all indicating it was likely used as a forge or metal-working shop.

Historical records tell us that Germyn Lynch was appointed warden and master worker of the 'Moneys and coynes' at Trim and Dublin castles in 1461, with his authority later extending to Galway, Waterford and Limerick. He was authorised to produce specific silver and copper coins, with the copper or brass coinage featuring 'the figure of a bishop's head' with the word 'Patrick' around it, and a cross with 'Salvator' on the reverse. By 1478, the Trim mint received permission to strike silver coins 'according to such fyness and alloy, as in the statute for that purpose is provided', though no further mentions of coining at Trim appear in records.

Curiously, despite the archaeological and historical evidence pointing to minting activities at the castle, no coins produced at Trim were recovered during excavations, and none of the actual structure survives today. The archaeological remnants provide a tantalising glimpse of medieval industry within one of Ireland's most significant castles, representing an important chapter in the country's economic history.