Another old photo from the 1980s and Carnforth steam museum. This is (I think) a hopper wagon that would have been used to transfer fuel from a coaling stage to the tender of a steam locomotive.
Some types of tub would run out along a short track until they we upended to coal the loco. This has bottom doors, so I assume ran out over the tender, the doors were opened and out fell the coal.
It's a pretty filthy manual business, which is why the railways struggled to retain staff and lead to the rush to dieselise. Steam locos might be romantic, but I suspect the appeal fades when you are up at the crack of dawn in midwinter to prepare one!