Llanwnda 3 was found during the restoration of St Gwyndaf's Church (NPRN 308468) in 1881. The restoration included the rebuilding of the nave, and the stone was incorporated into the fabric. It is built into the external north wall of the chancel, towards the east end. The stone is one of eight early medieval cross-carved stones associated with the church (see NPRNs 422430, 422431, 422433, 422434, 422435, 421734, 92655), suggesting it was an early ecclesiastical site of some significance.

The stone is probably a rectangular pillar (rather than a slab), of fine, igneous rock. Measurements are given as 84cm height x 24 < 30 > 26.5cm width. Only one face is visible. On its upper half is a linear Latin cross within a linear frame with rounded top. The carving is thought to date to the 7th to 9th century.

Sources include:
Edwards, N. 2007, Corpus of Early Medieval Inscribed Stones and Stone Sculpture in Wales

N Vousden, 12 January 2018