It is not. The slab, measuring 2.3 metres by 2.1 metres with a thickness of around 0.8 metres, is a boulder-burial, a prehistoric monument type found almost exclusively in the southwest of Ireland, in which a single massive cover-stone is raised on low support stones to create a minimal chamber beneath.

Two of those support stones are still visible here, holding the flat-topped cover-stone slightly clear of the ground. Boulder-burials are generally associated with the Bronze Age, though their exact function and the population that built them remain subjects of ongoing discussion. They are sometimes interpreted as grave monuments, though skeletal evidence is rarely preserved beneath them. What makes them distinctive from other megalithic traditions, such as the portal tomb or the wedge tomb, is their relative simplicity: no long passage, no elaborate forecourt, just a great stone balanced over a shallow space. The Letter By example was catalogued by Seán Ó Nualláin in 1978 and again by Roberts in 1988, placing it within a broader regional survey of this poorly understood monument class.