Many Ball mason jars have a number printed on the bottom of the jar, but this is a mold number that does not indicate the year of production. Rather, the mold number tells you where the jar was positioned on the glass-making machine that was used to produce it.

How do you identify Ball Mason jars?

Some helpful notes to keep in mind:Not every jar has their manufacture date on the glass, but most have the patent date. There will be a large number on the bottom of your jar. These charts tell you the approximate decade in which your Ball jar was made.More items •16 Aug 2021