What makes it remarkable is not its size but its iconography. Carved onto its smoothly dressed eastern face is a Latin cross, its upper portion framed by a single incised groove and its central junction marked by a small encircled equal-armed cross. So far, so familiar for early Christian stonework. But flanking the base of the main cross are two smaller symbols that shift the whole composition into something more specific and more unusual: on the right-hand side, a simple equal-armed cross; on the left, a T-shaped cross set on a triangular base. These are not decorative variations. They have been read as deliberate representations of the crosses of the two thieves crucified alongside Christ.

That interpretation was put forward by H. S. Crawford in 1926, and it lends the slab a theological precision that goes well beyond ordinary grave-marking. The T-cross, sometimes called a tau cross, is a form with ancient roots, and placing it beside a triangular base to distinguish it from the true cross of Christ suggests a carver working within a considered visual language. The slab itself is tiny, just 0.37 metres high and 0.25 metres wide, but the programme of carving on its eastern face is remarkably dense for something so small. It sits at the head of the row, at what would be the southern limit of the burial ground associated with the island's early medieval ecclesiastical site.