It was my dads he gave it to me about 30 years agn the base it says mason's cj with a circle on the side.then patent nov 30th.has a line under the th and 1858. it also has a zinc lid.It says zinc lid made for mason and its glass on the inside of the lid and it is cobalt blue.You can see bubbles through the glass.
tadpole,
It sounds like your describing a Consolidated Fruit Jar Co.piece.If you are, I do not believe they were made in cobalt.Dark cornflower blue,and sky blue,yes.Does the symbol look like this one?Also,there are a couple of jars in the blues mentioned above in the "jar talk"forum.Hope this helps. A.J.