OK then. Preserving its provenance is praise worthy. I'm glad you feel that way 👍
Not to downplay the significance and sacrifice of many soldiers, but Korean War artifacts are ubiquitous. They're absolutely everywhere. My parents allowed me to play with Korean War gas masks, field rations, uniforms, helmets, insignia, signal flags, and dozens of other military artifacts when I was a kid. Many of these items are still for sale today in army-navy surplus stores around the world.
I don't think it's a matter of preserving history any more. Preserve the ammo box, clean it, or toss it. It's your choice. No judgement.