Note the rock faces behind the gravel loader; they are representative of the rock which is being quarried somewhere off-scene from the 6.2.1. This quarried rock is then broken up and conveyed to the gravel loader for transfer to the Talbot hoppers.
In keeping with this rock, any other rock outcroppings on the 6.2.1 should be similar to the rock faces behind the gravel works. That is, they should be of similar texture and similar color to that found at the gravel loader itself.
Of course, I had two extra hopper crs, but they were not of the Talbot design, but were Märklin 8630’s, which are models of the Fals 176 hopper car of the DB: