When we pulled into a laeger or "DP" we would not use the can on our veh unless it had already been emptied earlier. It stayed, full, on the vehicle and we gassed up using what the echelon or the service battalion delivered.
To back up Rob Love's points we, the users and abusers of the mechanised artillery, (Rob will get the reference being a RCEME type
) hardly ever hung all our clag and gear on the outside of the vehicle because it would disappear. Our rucksacks were generally stowed outside 'cause, frankly, who wants my smelly, skid marked clothes? The veh stores (tools, etc were carefully marked and carefully locked in the carrier or SP gun to prevent the five fingered discount!
On rail moves everything went inside, even the sopping wet cam nets, to prevent pilfering at every little whistle stop along the way. We even had to gun tape the periscope glass as vandals would chip away at them with sharp rocks!
Congrats on finding a possible historical link between a wartime photo and and an actual artefact.
Cheers, Mike