Dirt. Rain is dirty, mud is dirty, if something was on the ground long enough for cardboard to decay, it's gonna be exposed to the elements. And segments of those bullets like the striking part which are indented would be awful to clean, just to shine up for a virtue-signal post.
Old brass and copper turn into a dull brown and eventually green given enough time and exposure to the elements. Think old pennies or the Statue of Liberty.
They wouldn't be near so shiny in that case.
[Please note, I am totally ignorant of firearms] Rust?
That's brass and copper you're looking at, so more like tarnish and dirt.
Dirt. Rain is dirty, mud is dirty, if something was on the ground long enough for cardboard to decay, it's gonna be exposed to the elements. And segments of those bullets like the striking part which are indented would be awful to clean, just to shine up for a virtue-signal post.
Old brass and copper turn into a dull brown and eventually green given enough time and exposure to the elements. Think old pennies or the Statue of Liberty.
There's even a term for it: patina.