When people come by to see my can collection, I remind them that there are 2000+ different cans. And then they proceed to point to my four Wild West cans and say, "Well those are the same." And then they get a can education.
Sure, they are all Wild West Sarsaparilla (whatever that is), but the cans are different.
This is an extruded steel can. Notice how the bottom is rounded and made of the same piece of steel as the body. Only the top is a separate piece of metal on this can.
And then there's the aluminum can. The bottom of aluminum cans is also molded from the same piece of metal as the body, only the top is a separate piece. And aluminum cans usually have some kind of recycle symbol on them.
If there is no recycle symbol, extruded steel cans and older aluminum cans can sometimes be hard to differentiate. So what's an easy way to tell which it is? Use a magnet! A magnet will stick to any steel can but won't stick to aluminum.
And now you've had a can education.