Peter are you sure about the Nentsberry loco?
As understood it all haulage there used horses, and indeed in the Beamish picture archive there is a photo of a horse pulling a waggon out of the entrance.
If one was abandoned underground then when I went through the workings in the. Mid 60's there was no sign of any, and we went a long way past Wellhope shaft.
In my opinion after the 'wind down' of the Nenthead operations, around 1922 these locos went as well, where to?
If this was not the case, in the re-working of the Jane Foot flats, they would not have used the winding system to pull the waggons, from the flats to Broomsberry level.
To quote the late Eric Richardson, the Wellgill level, having being stoped, underneath, sounded hollow, and the horses refused to go over it, and :happybday:they(the horses, know you know!)