Some jars were made in a dark green color to make contents like olives, for instance, more attractive to buyers. However, most olive green jars were made from batches of jars (often at the end of a day) that had impurities in itself. Consequently, these jars were fewer in number and due to their "imperfection" frequently discarded.
There are seven known spelling errors of perfect known.
PEREECT, PEPFECT, PEREFCT, PERFFCT, PFRFECT, PFRFECT, PERFEOT
Jars in amber, cornflower blue, olive green, etc. are worth more because fewer of them were made and they are in great demand by collectors. The amber jars were made that way as an attempt to keep fruit from turning brown, the color kept out the harmful effect of light rays on the contents of the jar. However, the jars were less popular with homemakers because the contents were more difficult to see.
And here's the jar we found Sunday at Goodwill. It's a display jar that was never intended for canning but was used in stores to display items such a pickles or beef jerky. Made in 1975, these jars are somewhat popular with some fruit jar collectors. It was produced in four colors: clear, aqua, smoky amber and cornflower blue. These jars are worth about $50 each. A smaller version of this jar was still made in the 1990s and might be found in restaurant supply stores
Did you know there's a red book to look up canning jar prices?