Yes I have & now I am kicking myself for not taking a picture. Two years ago I picked up an 8" diameter bowl, 3" height & while the bowl was cranberry, the cranberry was a casing over light green & the green reacted with a blacklight. In mine the thin casing & it was a casing not any type of flashing or stain had flaked away in an area about 1" X 1" round diameter exposing the green & you could feel the casing layer without problem with a fingernail. I picked it up dirt cheap, put it the mall to make a quick $20 & it sold immediately. One of the strangest things I'd ever run across & I showed it to a couple of other knowledgable glass dealers & they agreed it was a paper thin casing & was unexplainable.