Hi all!! recently a friend of mine bring me back from normandy a Patronenkasten 41 and a Wh belt, both of them in relic conditions, the Patronenkasten has some marks inside, anyone knows what these marks could be?

And which is the best way to clean up the two articles? the ammo box looks like it has some paint in the top, and i don't know if the acid oxalic will delete the marks. Any sugestion of how to clean the Patronenkasten 41 & buckle and what the marks in the ammo boxs means?
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Thanks!!!
Williamsong