It is not. The stone, roughly 64 centimetres tall and 30 centimetres wide, is coffin-shaped and bears a human figure carved in relief, most likely the image of a baby. An effigial tomb, in this context, is a funerary monument carrying a sculpted likeness of the deceased, a form more familiar from medieval church floors and cathedral niches than from the top of a harbour wall.

The sea-wall itself was built around 1800, and it seems that whoever directed the construction drew on whatever stone was available nearby, including what may have been carved grave markers from an older burial ground. About 500 metres to the west, at Ballyhack graveyard, there is a child-sized, coffin-shaped stone trough that could plausibly have served as the sarcophagus to which this carved panel once belonged. A second carved stone sits roughly 100 metres to the east along the same wall, and both pieces may have originated from that same graveyard. The precise history of how they came to be reused as building material is not recorded, but the practice was not unusual in an era when dressed stone was a practical resource and the sanctity of older monuments was not always a barrier to quarrying them.

The carved stone sits in plain sight along the inner, north-facing side of the wall at Arthurstown, visible to anyone who knows to look for it rather than through it.