This jar has significant repaired damage, but it's the only one of these I think.  There are a few black Hartell's around and one other black hartell's pint, but this is the only cobalt I believe.  It came from Al Vignon's collection and I have no idea how it got there.  I have never heard of one until I heard of this one in Al's sale.  A good size chunk is gone from both the lid and the jar, but even the fact that it exists at all is kind of amazing.  I'd love to have a mint version but until one turns up, this will have to do.