In the cataloguing of Irish field monuments, most sites fall into recognisable categories: standing stones, stone circles, cairns, megalithic tombs. When archaeologists use the term anomalous, they are signalling that a site resists easy classification, that its stones are arranged or present in a way that does not conform to any well-understood type. That ambiguity is precisely what makes Letterdife worth noting.

Letterdife sits in Connemara, a landscape already dense with prehistoric and early historic remains, where blanket bog has preserved, and in some cases obscured, centuries of human activity. Stone groupings in this part of Galway can represent anything from the remnants of a collapsed megalithic structure to the boundary markers of a long-vanished field system, or occasionally something that has no obvious parallel elsewhere. Without more detailed documentation currently available for this specific site, its precise character and date remain uncertain, which is part of what makes it unusual even among unusual things.