The stone is 20 paces north of the track roughly half-way between the corner of the wall to the west and the start of the rectangular enclosure to the east. GPS reading SH 6801 7207. It lies low to the ground and is 2.75m long N-S and up to 1.0 m wide E-W.
There are a group of markings on the SE side of the stone, including a wigwam shape. The incisions are up to 12 cm long, 2.5 mm wide and 2 mm deep. This area of the stone looks as though it could have been smoothed and there are 4 or 5 little holes that look a bit like punch marks. The initials R.R.P. are directly above the wigwam shape. There could also be other incisions on the other side of the stone but they are less clear.
The incisions in the main area are shallower but clearer than those on other so-called arrow stones in the area. The Gwynedd Archaological Trust class it as a medieval inscribed stone and I suspect that it is not older than that. The RCAHW Caernarvonshire inventory from 1956 describe it as "an earthfast stone about 8ft by 3ft with a small group of grooves on its upper surface" and both sources give the grid ref as SH 6800 7206. My GPS reading is a bit different from that but the description matches and so I think I've got the same stone.
"Cerrig Saethau (Arrow Stones) near Llanfairfechan" by W. Bezant Lowe in Proceedings of the Llandudno and District Field Club Vol. VII 1912-13 pp. 61-65 gives the following description:
"This is of very fine grain, of irregular outline, and measures 8 feet 6 inches long by 3 feet 6 inches wide; the direction of its length is NW to SE. A small part of the surface, measuring 12 inches by 8 inches, and situated 8 inches from the SW side, and 3 feet from the SE end, has been smoothed, and on this are most of the grooves, but a few may be seen near the NE end of the stone. The marks vary from 7 inches to 4 1/4 inches in length and from 1/4 inch to 1/8 inch in width; they are 3/16 inch deep."