"In two instances the decoration consisted of simple shallow, pecked cup marks but one slab was far more intricately decorated. On this slab there is a perforation – worked from both faces – a cup mark of similar radius and a probable third cup surviving at one edge of what was once a presumably larger stone, all seemingly pecked."*

Fascinating; are there any other instances where decorations are worked from both faces and actually perforate the rock?

* http://www.headlandarchaeology.com/Projects/Balblair_cairn/Headland-Archaeology_Archaeological-