I have not been able to find out much about bottom markings on the Ball Jars except for a number 2 ect...
What is this one for, is this to mean the number 4? or am I way off.
On blown jars the base markings can vary widely from numbers to symbols.These markings identified the blower and team.So at the end of the day they could do a count and get paid. On machine made jars it was more of a quality control thing. Identifying a mold or machine used in a particular jar. That's my story and I'm sticking to it.[]