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Many items come from online sellers in Charleroi, Pennsylvania, whose family members worked for Corning Glass Works during the years of opal PYREX production. The items were most likely production mistakes which occured during the transition of manufacturing one product line to the next. Since most "PYREX with a Twist" items come from Charleroi, PA, it's possible that plant workers brought home these "mistakes" or perhaps they were even sold in a company store at a discount.