Check the jar from top to bottom. The Kerr name will be embossed on the glass. There are some general guidelines to approximate the date of a vintage Kerr jar between 1915 and 1930. The finish on a fruit jar can tell you roughly about the date it was made.

How old are Kerr canning jars?

These jars were made from 1904 until World War II, when they were discontinued in favor of the Kerr Glass Top. The line was reinstated about 1946, and production continued until at least the 1980s. All of these jars had the Mason beaded neck style, although the actual seal was at the lip or rim of the jar.