The emerald green flaccus is definitely one of the prettier fruit jars.  While they aren't exactly common, their price is more due to their beauty than their rarity and they aren't that hard to obtain.  This color is extremely rare in jars and definitely reaches its highest point in this jar which leaves the emerald Safety Valves in the dust aesthetically.

This is a pint jar as are all flaccus jars.  I guess nobody wanted a quart of catsup.

Flaccus jars are actually product jars which, in jar lingo, means they held a commercial product originally.  Under this definition, however, many jars which are not normally thought of as product jars actually are.  There are many examples of old masons with labels on them for pig's feet or oysters (apparently two delicacies from yesteryear).  For this reason, I don't really think too much about the product jar/fruit jar "distinction".  I think it's a distinction which really doesn't do much distinguishing.  A bit like talking about the class of "dogs with 10 legs".

Flaccus, however, sold Catsup and I believe other condiments in their jars (umm - I bet red catsup looked tasty in this emerald green jar!).  However, they have the words "Fruit Jar" on them and are definitely accepted as fruit jars.  In fact, there are entire collections devoted to Flaccus jars and with some people they're a bit of a cult favorite.  They come in many different variations.  In addition to the steers head shown here there was an elks head.  Those jars have a glass lid and zinc band and are far less beautiful than these with the glass lids in my opinion.

There are also some imitators which are much rarer than the Flaccus but without the cult following and crazy colors, those imitators are not as popular.  By the way, I say "imitators" without really knowing whether this is the case.  For all I know, Flaccus may be the imitators, although I think it unlikely with the wild success of Flaccus and the more modest success of the others.

For a related jar, see the amber flaccus.