What Do the Numbers Mean on the Vintage Ball Mason Jars?

Ball brand mason jars were originally produced in 1884 by the Ball Brothers Glass Manufacturing Company (now simply called the Ball Corporation). The Ball brothers who owned that company began to make glass fruit jars when the patent on the Mason Improved fruit jar expired. The earliest jars made by Ball were colored amber or aqua and were produced in the company's glass-works in Buffalo, NY. Ball jars are now manufactured by many different companies around the world that simply use the Ball name for branding.

Ball jars were originally formed by professional glass blowers who were each supported by a small team of assistants. The glass blower would mark all of his jars with a number used only by him. This was done for payment purposes. At the end of the day, the glass blower and his team would be paid for the number of jars that were marked with their number.

Later, when machines were used to make all of the jars, each of the molds that the machines used were marked with different numbers. This helped the plant manager to maintain quality control, as each machine used at least four molds each. If one of the four or more molds had a defect, and there were several machines running at a time, shutting down each machine to find the defective mold could waste hours of precious manufacturing time.

Modern Ball mason jars are marked with many different numbers, and those numbers vary by the company which is manufacturing them under the Ball brand name. The numbers can refer to the plant location, the job or batch number and the date of manufacture.

The earliest Ball jars, which were hand blown, are easy to identify because the bottom of the jar will have a mark called a pontil scar. This comes from the point where a metal rod was attached to the bottom of the jar for cooling while the blowing rod was broken away from the mouth of the jar after it was formed. This pontil scar may look like a ring of raised glass or an indentation that is colored black or red.

If you are attempting to guess the date that a jar was manufactured, the location of seams in the jar and the smoothness of the top are both helpful indicators of its age. If the top of the jar is rough, it was hand blown either freehand or into a mold and the top was broken off the blowing rod and ground down for smoothness; this means it was probably made before 1900. If the seams stop short of the lip, that means that the lip was attached to the jar or the top was formed after the jar had been blown into a mold. This type of jar dates to before 1915.