What can still be read amounts to a handful of words: DALTON, 29 AUG, ANNO. Yet local memory has preserved what the stone itself can no longer say clearly, and the reconstruction of the full text points to something that adds considerable weight to an otherwise unassuming site.

A mass-rock is exactly what it sounds like: an outdoor altar used for Catholic worship during the Penal era, when the public practice of Catholicism was suppressed under a series of laws enacted from the late seventeenth century onwards. Priests who continued to say Mass risked severe punishment, and congregations gathered in remote or elevated spots where approaching authorities could be spotted at a distance. The hillside position at Mullaghcloe, commanding views in all directions, would have served that purpose well. The limestone slab embedded in the masonry, measuring roughly 52 by 42 centimetres, appears to be a memorial fragment. When J. Mc Cabe examined the site in 1971, the inscription was already largely illegible, but local informants provided the key detail: that it commemorates a priest, Fr. Dalton, killed during the Penal period. The reconstructed Latin text, pieced together from the surviving letters, reads as ME FIERI FECIT JOANNES DALTON, SACERDOS, dated 29 August, Anno Domini 1689. That phrasing, meaning roughly "Joannes Dalton, priest, had this made", suggests a memorial erected by the man himself or in his name, which places it in the same year as some of the most stringent anti-Catholic legislation in Irish history.

By the time the site was revisited in 1984, it had fallen into neglect. The iron cross that had stood at the back of the altar was gone, the wooden gate broken, and the whole structure overgrown. A short distance to the north-east, about five metres away according to the Ordnance Survey six-inch map, lies a feature recorded as Sunday Well, a name that carries its own suggestion of informal, semi-clandestine religious observance. The pairing of a mass-rock with a holy well is not unusual in Ireland; both belonged to a landscape of worship that operated outside official structures, shaped by necessity rather than architecture.