Revisited today - on the northwest face, in the centre is what appears to be a cupmark - didn't notice that last time I was here but that was a while ago. It's not a recent addition - I think I mustn't have been wearing my glasses last visit! I've appended a photograph which shows it reasonably clearly.
Leave Perth on the A94 towards Scone, and take a right turn towards Murrayshall. Follow this road out into the country heading north east until you pass the golf course on your right - look to your left and you will see the stone in the centre of the field.