just got my first delivery. used a chisel as suggested, and peeled back enough to get a small carton out. the ammo is in pristine condition. as a matter of fact, when the first chisel stroke broke through, there was that "sssssssssss" sound that comes from opening an airtight (or sealed, like a vacuum pack) container.
it smelled really cool; old, but clean. kind of machine-shop-ish. I am totally stoked. going to shoot some at the range tomorrow. if it's cool, which I have little doubt it will be, I am going to order as much as I can without the iwfe kicking me out of the house.