Interesting find Nappy.
Can you share some context to it? Where it was found (not location but setting/environment) , photos of placement in situ (blur landmarks if necessary)
Possibly some pictures with size reference, I can tell its sitting against an upholstered back of some sort.
I am no expert, but I would like to see more of the rock and story. I am wondering as to the additional marks to the left of the "x" as part of the overall mark statement. Is the 'X' incorporated with a long legged Cross on its side. additional distant photos would assist in better speculation.
Thanks and look forward to anything additional you can share.
-N-