The following comment was left on "Anglezarle Misc 8" which I think describes this stone. Explains the carvings and that the stone was standing 100 odd years ago...
"Sadly, much nonsense has been talked about with regard to these stones.
There was a man called Andrew Mather who would have been about 120 if he was still alive today. Some 45-50 years ago he told me that when he was a boy, he had two friends and they called themselves 'The Triangle Gang.'
One of their favourite places to meet and camp was a small depression towards the southern end of Stronstrey Bank where there was a fairly tall upright stone. One of the boys carved a small triangle on the face of the rock as a symbol of their 'club.' Some time later, they carved a much larger triangle on the same rock."