"Hex" Threads
From Insulator Wiki (Wikilator)
Lee wonders if this is some sort of anomaly made from the mechanism that would retrieve the threaded plunger (the size of a wooden cob -- just the tip, not the entire shaft) out of the molten glass.
Per Brent's observations, these "globs" on the base of the threads only appear on very end game glass -- the rolled-under base toll, the No 31 Keg, the signals and B 44. It is most certainly a molding problem and not intentional or desired.