This standing stone at Sallybrook measures 1.62 metres high, 1.07 metres wide, and 0.33 metres thick, oriented along a northwest to southeast axis. Like many of Ireland's prehistoric monuments, its exact age and purpose remain tantalisingly uncertain, though such stones typically date from the Bronze Age, roughly 2500 to 500 BCE.

The stone bears an intriguing feature that hints at its significance to ancient peoples; near the centre of its western face, archaeologists have identified a shallow depression approximately 0.7 centimetres in diameter, which may be a cup-mark. These enigmatic carved hollows appear on numerous prehistoric stones across Ireland and Britain, and whilst their meaning is lost to time, they're often interpreted as having ritual or astronomical significance. Some researchers suggest they may have held offerings, marked celestial alignments, or served as territorial markers for Bronze Age communities.

This particular stone was documented in the comprehensive Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983, which catalogued the county's archaeological heritage from the Mesolithic period through to the 17th century. Standing stones like this one offer a tangible connection to Ireland's prehistoric past; silent sentinels that once held profound meaning for the communities who erected them, whether as burial markers, meeting points, or elements in a sacred landscape we can only partially reconstruct today.