I think there is as much (or more) to learn about marble-making from marbles that experienced some challenge during their manufacture. They make us look at the glass and appreciate it, see the motion and think about what was going on. For me - those "flaws" made me more interested in the machines, the pots, the cullet, the sand, chemicals, how the weather can affect color striking, glass compatability, machine component wear.... the list goes on.
Those issues get us out of the constant drone of "What is the name?" and "Is it rare?" and deeper into the history, process and reality of the fact that these were kid's toys made for fractions of a cent. I see the first photo and start thinking about what was going on in the glass.