BG,

The factory 'stones' are stepped and sit on top of the outer edge versus being recessed. The pic below is a side profile shot of a genuine 'Cobalto' stone* and you can clearly see the smooth transition from the stone* to the nut. The second pic is of the craft store variety and it too sits on the outer edge but it not a 'stepped stone. A properly sized stone should cover the entire edge and be flush with the sides of the nut.