Well, yes... and no!

:angel:
I'm pretty sure I know the ones you mean and mentioned to the seller that I was certain these were not made by Chance. There have been other cases of lampshades being wrongly attributed to Chance, but after discussing this with the former general manager (1959-81), he confirms the only ones Chance made, were experimental and merely involved modifying large 7-in handkerchief vases with a hole drilled in the centre. Good idea, but Chance never progressed this.
BUT, before everyone sneaks off and starts wrecking perfectly good handkerchief vases, there were only a
very few converted, and probably none that ever survived (apart from one in aforesaid gentleman's garden, which he kindly dug up for me as proof!

)
So if any of these converted vases do ever appear, I would be extremely sceptical that they were genuinely intended to be lampshades.