Doug Spiers, the local county archaeologist, hasn't commented on these yet but did say the incomplete one may give people a much better idea of how these were produced. It did look a bit (to me) as if they had been 'picked' out with a pointed stone or similar. The complete one isn't quite as smooth as some of the Kilmartin ones, but it's in a very sheltered spot and so may not have become as weathered as the Argyll and Perthshire ones. It's a beauty though isn't it?