For anyone working through such maps with an eye for anomalies, that symbol carries a question: what exactly is it marking?

The answer came in 1983, when an on-the-ground inspection confirmed the feature to be a quarry, almost certainly worked at some point after 1700. That date matters administratively, since sites of post-medieval origin fall outside the scope of formal archaeological survey in Ireland, which focuses on earlier remains. The quarry at Ballyterrim therefore occupies a slightly awkward position in the documentary record, old enough to have made it onto a mid-twentieth-century map revision, but not old enough to attract the kind of systematic attention given to ringforts or megalithic tombs. Small rural quarries of this period were typically used to extract stone for local building, field walls, or lime burning, and they rarely generated the paperwork that might tell us who worked them or when they fell out of use.