St Davids 17 is a rough, unshaped, approximately quadrangular pillar of gabbro. . It is now located in The Lapidarium at Porth y T'r, St Davids Cathedral (NPRN 306). The stone was first discovered around 1875 when it was in use as a gatepost at the south-west corner of the field known as Parc-y-Berth, to the north of Penarthur Farmhouse. It is thought to have been moved to St Davids Cathedral in 1885, and was moved to the basement of St Mary's Hall in 1994, and to its present location in 2000. The stone is one of four (see NPRNs 423520, 423521 & 423522) in the vicinity of Penarthur Farm, the location of a possible chapel and cemetery site (NPRN 423519). The stones are generally accepted to have been originally placed upright around a holy well to the east of the small parcel of land belonging to the Bishop and known as Maenarthur, where the stones were first recorded. It is unclear whether this was Ffynon Penarthur or Ffynnon Parc-y-Berth.

Dimensions are given as 128.5cm height x 45 > 25cm width x 46cm diameter. There is a gate-hanger hole near the top of faces B-C. The stone is carved on one of its narrow faces with a lightly incised Latin cross, which is situated near the top. The carving is thought to date to the 9th- to 11th-century.

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

N Vousden, 30 October 2018