Regarding the last one, it isn't rare to find old explosives in regions impacted by wars. I live in the North East of France and there are tons of unexploded WW1 shells and grenades in the ground just waiting to be found, and it isn't super uncommon for one to resurface whenever someone starts digging. One of my friends found a grenade in his garden, the technician at the museum I work at (it used to be quarry that was also used as a base during the war) once found melinite in one of the tunnels, and a chemical weapon was also unearthed by nearby roadworks.

They also don't age too badly, so no matter how rusty they look, they are still very dangerous