Di Pattison describes this character (p.266) as "the archetypal sad old man, as if peeking around a lump of stone". I came across this face unexpectedly by moonlight, my independent recognition of the carving confirms Pattison's.

However, I interpret this gimlet eyed glare as something altogether malign - dark and intimidating rather than sad. Its worth noting that this large right looking sculpture has a counterpart carved on the other side of the same monolith (visible here). These faces appear as if they were intended to balance each other, as if they were related in some way, characters from the same lost myth perhaps.

The face shown below is in fact the left of a duo of carved characters standing side by side, Martin Ringer shows them extremely well on p 312 of his book.