When originally discovered this motif appeared to have five rings curtailed by the edge of the rock ,see http://www.themodernantiquarian.com/post/53565 ,
quite a common feature in rock art . However ,when the the area surrounding them was cleaned up a bit and with better lighting the " rings " turned out to be two sets of arcs giving the impression of rings . While there are lots of examples of rings being cut off at a fissure or or change in slope or texture I don't know of any that have it on two sides .
A new motif found yesterday plus some examples of incisions . Quite a few of the marked rocks in the area have multiple incisions but rarely across the motifs . Despite this my first explanation would be defacement . The incisions are not at all similar to the "Arrow Stones " or like those found at Balendune.
Some new finds from today , the blue stone in one of the pics is fist sized ,very hard whinstone with signs of percussion marks in the centre It could well be the hammerstone that was used in the the carvings.
Last weekend I found a stretch of rock with some cup marks and an incribed name , Alexander Crerar , on the same rock .Sadly there was no date but a wee bit geneaological research came up with a local who had written in journals in the early 1800's . I like to think this may be the same chap , if so he would be one of the early rock art researchers . A return journey this weekend produced seven new marked rocks , not bad for a quiet glen that had no previous recorded prehistory .