Its existence is known largely through a single document, and its physical remains, if any survive, have not been pinned to a spot on the ground.

In 1621, Edmund Medhopp received a royal grant that bundled together a curious assortment of properties: the former friary of Athlone, four cottages, seven acres in Caltre, two fishing weirs on the River Shannon, and one water-mill in what the document calls the town of Mollinemeaghan. The grant is recorded in the Calendar of Patent Rolls of Ireland for the reign of James I, and it speaks to the way dissolved ecclesiastical and monastic holdings were redistributed in the decades following the Tudor plantations, often packaged with working industrial assets like mills and weirs. A water-mill of this kind would typically have been a grain mill driven by a wheel turned by a diverted stream or millrace, and its presence alongside fishing weirs suggests a small but productive riverside operation. Whether Medhopp's mill was already old in 1621 is not known, but the possibility exists that it had medieval origins predating the grant. The Ordnance Survey's six-inch map of 1837 marks a corn mill in the same townland, and it may well occupy the same site, though that connection remains unconfirmed.