The cobalt Mason's Improved comes to me from George McConnell who first bought it, then it was in Al Vignon's collection and finally sold through Greg Spurgeon.  It's a venerable old jar.  On the back it says "Clyde, NY" and there are people who collect stuff from Clyde, NY who would like very much to have it.  It's the only example anyone knows about.  I remember hearing about it when I first started collecting as some sort of "holy grail" which of course I would have been extremely honored just to be offered a glance at it someday.  Funny how things turn out sometimes.

The "CFJCo" monogram on the front stands for "Consolidated Fruit Jar Company" which was one of the big producers of jars back in the 1880s or so.  If you ask somebody more knowledgeable in the hobby, I'm sure they'd be able to rattle off the dates and history of the company.  Many, many jars have their monogram on them, including a series of modern reproduction half gallons.

This jar went up on the auction block just shortly after I started thinking about how this was one particular cobalt jar I'd never own.  So you never know.  Something may fall from the sky when you least expect it.