can't speak to the stone atm, but the reason the Essenes (or anyone else) would refer to an anointing oil as 'chrstos' is b/c etymologically the root word in greek (chrio) we translate 'Christ' means literally 'anoint' or 'smear' (with the idea/picture of touching with the hand). So it is like calling the anointing oil 'anointing oil'.
Unfortunately too many believe/been taught that 'Christ' is a 'name'…actually it is a description of office.