I believe this buffer stop marks the extent of the coal drop / siding behind what is now Kilfrost [aka Albion Works]. {It faces west, towards Haltwhistle Station, and part of the route appears to have been excavated away}
Note : I have been told that the Varnish Works - a little further east from here - was also served by a siding from Haltwhistle Station, but that route is not obvious "on the ground" ...
Ignoring the 2ft line that served the quarries on Hadrian's Wall with a route alongside the Haltwhistle Burn.