I have a Ball perfect mason jar with the 13 on the side. September 17, at 5: November 26, at 9: I also have a quart size Ball Perfect Mason, square, with 13F on the side and bottom. I appreciate you sharing your knowledge!
There are no other numbers on it.
The Collector's Ultimate Guide to Canning Jars
Catharine says: Inspect the jar for mistakes. The quality control people used the number on the bottom of the jar to identify which mold was producing bad jars. Enjoy this post? Thank you for your understanding and support!