This is a HG light cobalt FCG Co wax sealer (FCG Co is embossed on the base).  It is a rare jar but there are a few of them around.  It's rarer cousin is the distinctly colored dark cobalt version here of which there are only two known.  It also comes in a deep cobalt quart version as shown here but I'm unaware of any quart versions of these in a light or medium cobalt.