The stone in question was recorded as bearing a cup mark, one of those shallow circular depressions ground into rock by prehistoric people whose precise intentions remain unknown. Cup marks are among the oldest and most enigmatic forms of rock art found across Ireland and Britain, appearing on exposed boulders and outcrops and dating in many cases to the Neolithic or early Bronze Age. What makes Ballykean unusual is not what survives but what does not.

The geologist George Henry Kinahan, writing in 1884, described a large flattish stone sloping to the south-west, with a single cup mark near its upper margin. He noted several other stones nearby, though none of those carried cups. More significantly, he recorded that most of these stones had already been split, and that others were said to have been broken up and incorporated into the fabric of Ballykean House, its farm buildings, and its surrounding walls. The carved rock, in other words, was quarried for convenience, its prehistoric markings absorbed into gate pillars and field boundaries without ceremony or apparent notice. When the location Kinahan identified was checked in 1990, the stone could not be found at all.