Donald's Grave is apparently the name of this boundary stone on the south side of the minor road that runs from Kiln Pit Hill on the A68 to Blanchland, 10m east of the Coal Road (track) that leads north-west through the grounds of Slaley Hall.
The stone is Grade II Listed (List Entry Number: 1045376) and is described as:
"Probable boundary marker, C18th or perhaps a reworking of a more ancient stone. Gritstone. Roughly-cut monolith of trapezoidal plan, exposed height 0.9 metres. East face with incised B; north face with remains of incised design, possibly a cross within a circle; west face incised A (laid sideways) and S."
See closer photo here
NZ0054 : Donald's Grave near Esper Shields (detail)
Local researchers think the stone may be an allotment marker from the Bulbeck Common Award (1771) which was divided between George Silvertop of Minsteracres (S) and George Baker (B), the Lord of the Manor. It has also been suggested that Donald's Grave may have originally been mapped on the north side of the road but the nature of the feature represented by the name is not specified.
There are two further named stones just to the north, possibly on the same boundary: Greyhound Stone (which I couldn't find) and Hare Stone, an C18th boundary stone.
All 3 stones are named on the 1st Edition 6" OS Map Northumberland, 104 (1864):
Link
Only Donald's Grave is represented on current large scale mapping.
The Hare Stone is also Listed Grade II (List Entry Number: 1370318) said to be marked B (Blanchland) on south-west, and S (Slaley) on north-east side
NY9955 : The Hare Stone near Slaley Hall
The hill in the field beyond the wall is named Hairy Side.