Hi
Thanks for posting, this is a great question.
Yes, you will find a number of Atlas EZ Seal jars listed in the Red Book of Fruit Jars which list out various numbers (likely mold numbers) and other variations of embossing on the base. Some jars were marked "SEAE" instead of SEAL
Thanks to the internet, and just the advancing of collecting, there is a lot more interest in mold variations.
Some of them collectors care about, others not so much. One thing I can say as a collector of over 40 years - people often get more interested once someone documents all the differences.