Best way to access these fellas is to take the john Breckon Road and then walk up the Skinner Howe Crossroad. You'll see the stones on the hill above you.
You need to leave the path to access the stones. I was only there for five minutes and a keeper came zooming over the moor in his eight wheeler. I was well impressed with his vehicle it looked like a big green banana split's car but with an extra two wheels and a rifle. We had a brief discussion over the state of the grouse and how much grit he had to leave on the moor every day 'because grouse have no teeth', then I asked him about the marks on the stones. He confirmed Graeme C's theories and deflated my dreams of finding new cup marks.
The stones are about three feet high and command lovely views over Westerdale and Baysdale. One of the stones is covered in 'pseudo-cups'- bullet wounds to you and me, apparently they used 'em for target practice in the war.