Its hard to see from the tiny picture - id appreciate a full resolution one if you could send me a jpeg ? But from what I can see, the mark shaped like 'R' is visible and this is usually associated with travel, journey or a passage. This could be a reference to the passage of the spirit into the next world or literally a waypoint for a traveller on the road. The lichen appears to cover the incisions, so it doesnt look recent. Earthstepper will probably know best.