How do you date Kerr self sealing jars?

A number is usually embossed on the jars bottom, dubbed a mold number. This will refer to the blower and his team. A mold seam means the jar is post 1915. Look for small scars at the bottom and look to see if the design is more modern. This means it would be post-1930, during days of more efficient machines.

How do you tell how old a canning jar is?

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

Are Kerr jars valuable?

Typical values: The value of antique Ball, Mason and Kerr canning jars varies greatly. Typical prics range from $8 to $25 a jar.