Just thought I would let you know Derek Crouch operated 14 of these Cat DW/PR21 Athey wagons in the 1950s.They were loaded by a Ruston Bucyrus 150 electric shovel.
Photos of these can be found in the book by Bill Huxley, Titled, Opencast Coal,Plant and Equipment.
Hope this is of some help.
![Very Happy :D](./images/smilies/icon_e_biggrin.gif)
Regards from Canada
Mark.