Regarding the Spiderweb bowls (assumed to be dessert bowls, which never had lids), I have found very rare examples with a birdbath base, but not yet in clear. The ones noted so far were a large amethyst bowl and a smaller graduated opaline bowl - both like hen's teeth. They both have the hallmarks of Spiderweb, but no-one can determine how, or why, they were made. All of Chance's pressed domestic glass output was clear, so these two anomalies are very, very odd (see p.17, my book).
However, the appearance of a clear model, if it conforms in dimensions to the others and has the same seam marks, could possibly clinch it as definitely being made by Chance. A good find from a technical stand-point!
MODS: is it worth splitting out the 'swan' posts? Thanks.