I've heard many people collect the blue jars, I have some but don't know how to tell if they are old, worth anything etc. Give me some ideas and who knows I may list some:)? One person told me that people put them in the sun with blue food coloring , let them stay out for days then pass them off as old. I doubt this is the case with mine, most of them were from my mom who dies last year and she was 83, canned her whole adult life but I would never want to take a chance and mislead anyone just in case. I can but figure the clear ones work just as well for me. I also have some really odd "square" ones etc.
I'm not real knowledgable.I do kno the number on the bottom represent s how they were issued. The square ones with like grips on side are also old. I quit canning with the blue and square ones.lower numbers are the oldest from what I kno. Which is limited. LOL