While checking the ground of a former WWII work camp in Germany with a metal detector I found this thing:

Part of a backpack clasp?

Of course it might be just something from the camp, but in close vincinity I found the remains of lemon juice and coffee powder bags from US K-rations. So it might have been some army gear.

But it's not necessarily US gear, since this part of Germany (NRW) was occupied by British Army. Maybe they were just using the K-rations for the former prisoners.