This jar is a deeper blue/aqua than my others. I can't figure out what the number on the bottom means, or if it is a number. The top with concentric circles is also unusual.
ROSANNA...Welcome to the Forum.
The base number is most often referred to as a mold number. AS designs changed or molds wore out/broke, new molds were made and a numbering system was used to keep track of the items made in each mold.
As for the concentric rings: Your jar an Atlas jar? I see those type lids on more Atlas jars than others, but the lids were inter-changeable and could be used on other jars of that type...
I'm sure my descriptions will be misleading, so i am attaching a photo of each bottom. The wierd "6" is a ball Ideal and the "d" is a Safe Seal" thanks.