This one wasn't in a kiln, Machine made. The hot glass was in a tank before it came out and was sheared off dropped and hit the rollers. Yes they are called annealing fractures, probably from cooling to fast ?? Not sure, maybe someone else will chime in ?? There are a few different reasons they get these fractures. Fried marbles is a term used to describe marbles that were heated after production then plopped in cold water fracturing the entire marble clear through, they were packaged and sold as "Fried marbles" many people did it at home, it used to be a thing I guess ??
https://www.instructables.com/Fried-Marbles/
Another Josephs coat, I had almost 400 of them at one time cut it down to all of them, @ or over an inch. This one was 27/32nds. My favorite type of German hand mades.