i have two identical sets of three, one purchased initially and the other purchased as part of a bundle with an ICI shunter a few years ago.
I could have tried to renumber one set, but instead decided to have one set empty and one set loaded. I weathered both sets then added sheeted loads to the other set.
The sheets were from a Parkside Models PA60 Wagon Tarpaulins kit I had in stock from doing other wagons a few years ago. The kit was of 8 BR tarpaulins, so I just removed the BR markings etc. with a black felt tipped pen.
Unfortunately I could find any photos of these wagons loaded, but I assume they would have been used to transport rock salt for road use etc. and would have been sheeted to prevent rainwater dissolving the salt during transport.