The grid ref given here is that matching the spot where in 1913, an oak coffin was discovered during ploughing. It’s 1.67m in length and contained a few teeth, remains of stitched calf skin, a drinking cup and flint scraper. Radiocarbon dates of 2400-2200BC were determined, suggesting an early BA date for the burial.
the C&R stone does not seem to have been part of this burial, but it’s exact findspot is unclear.
There is a model of the coffin, along with a drawing of it, in the "archeology room" at Bamburgh Castle, just through the castle shop in the first display case on the right hand side.