To the best of our current knowledge, only one pot of cobalt blue ever got melted and used and it was while Michael Harris was still there.
I don't know how many pieces had just little bits added in, or large amounts for thick use.
But we must be coming close to having found just about all of it.

But as it is unmarked and not catalogued in any way, it does depend a lot on folk having hunches and recognising the quality to get them dug out of their obscurity.