The 2013 Challenge, day 14: Forfar to Whiting Ness (7)

On the right of the road into Letham there is this rather interesting feature, which turns out on closer investigation to be a cup and ring marked stone. Now normally, when one of these is marked on the map, I am completely unable to find it on the ground. On this occasion, however, there is no difficulty about finding it on the ground; but there is absolutely nothing on the map to indicate that it is there!