I bought this jar not too long ago on Ebay.  I've wanted one of these jars for quite a while now.  The monogram you see on the back is HGW which stands for Hero Glass Works.  Part of the appeal of this jar is its rarity but a big part of it is that the monogram is so beautiful - at least that's a large part of my decision to buy.  Also, there are people out there who specialize in Hero Glass Works items which drives up the price a bit.  This is a mason and it's front embossing is the standard "Mason's Patent Nov 30th, 1858".

Reverse embossed amber masons are generally desirable items in the collecting community.