In reply to Dave Warburton:
Kebs= Bridestones above Todmorden (there's another Bridestones in Yorkshire).
It's
not chipped, it's erosion from use. The chips you refer to used to be smears and these have enlarged with usage. The nature of the rock means it has a hard shell, under which is soft grit. Once the shell is broken it erodes very quickly, with the result you have seen.
This problem is much much more likely if you climb there when it is even slightly damp.