I've only heard theories, although some state them almost as fact. I think the general consensus is that they were unintentional but who really knows. I mean if the flow from the tank slowed down but the cutter speed remained the same, you would have smaller marbles. The slower the stream, the smaller the marble, until you slow the cutter speed down too. Then when you slow it down to match the amount of glass flowing from the tank required to make a 5/8" marble, you get a swirl instead of a patch because the stream ran longer and was able to fold and loop instead of just get cut off like short blocks of cord wood. Then when it hit the rollers, it all got smoothed and rounded into a sphere. So I don't see how it was unintentional for MK to have made 5/8" swirls... it's not like one marble could have come out as a patch/ribbon and the next a swirl. Sure, maybe it could get grabbed by the rollers and twist a little but it wouldn't be more than a little, like the jabo classics when they get caught by the rollers. Some of the MK swirls have an actual stream of glass that looped over on itself more than once and long enough to fill the volume required for a 5/8" sphere, which means the cutters were slowed down as well. I don't think that happened unintentionally unless it was during setup and adjustment periods. That's my take on it, based on mechanics and my understanding of how the marble making machines work. Someone correct me if I'm wrong please