Hazel Atlas glass production question

These two Hazel Atlas iced teas have small rough spots at the bottom center on the inside. It resembles a rough pontil scar. I'm guessing this is a mold mark / flaw of some kind, but can't imagine what type of mold would leave such a mark. Or perhaps the mold left an extra bit or nub of glass that had to be removed?

Just curious & wondering if anyone had any idea. Thanks for looking.

 

Damaged or poorly cleaned plunger come to mind.

 

Thanks George - do you mean, the plunger that pushes the formed glass out of the mold?

 

No that would distort the glass also a mold is two or more pieces of metal that is clamped together often around a base plate. A gather of molten glass is placed in the mold and pressed against the pattern sides either with air or by pushing a plunger into the gather and forming the patterned item. Hazel Atlas did not use air like Federal or modern bottle makers. These may well have been automated so that a damaged plunger would not have been caught right away.

 

I understand - thanks again. I've seen several videos of people using metal molds to form glass pieces (in a couple of the Blenko documentaries, for example), but I haven't seen one with the details of how completely machine-made glass was made. I appreciate the info.