The picture is dated 1890. The wagon is very similar to ours but has square shaped wooden buffers. The end door and other features appear identical.
End tippling was a pretty cumbersome process involving one wagon at a time being shunted along a siding to the tippling apparatus and back again before the next could be offloaded. Much more common were the side tipplers whereby an entire train load of wagons could be tipped sideways one wagon at a time without being separated from their train.
The end tippler had the advantage that the wagon did not need to tilt very much for the load to slide out. Side tippler machinery required a much steeper tip - in fact a near inversion of the wagon:
In this instance the wagon contents of coal drops into a pit, thence to a conveyor belt to the top of the coaling tower in the background to be dropped into the tenders of steam locomotives. In some cases entire loaded wagons were hoisted to the top of the coaling tower to be tipped: