Ok well I always thought that bullseye washers were all the dome washers I see, but I am beginning to think otherwise after reading through a few post.

So what exactly makes it a bullseye washer rather than a dome washer setup? Is it the placement of flat washer and dome washer that makes it bulseye?

Also, are the vintage bullseye washers really stacked? or is that just a fold in the metal that was made during its making? If this is not what was meant by being "stacked," what are people referring to?