From 1947 until approximately 1959, the lids' tops had longitudinal ridges flanking a smooth middle, and had smooth undersides.
After 1959, the top surfaces were smooth and the undersides were fluted lengthwise.
Any 4-quart #404 bowl in a color of other than yellow must therefore be dated no earlier than 1949.
The design of #500 series refrigerator storage dishes' lids can help determine their age.
It was not until a few years later that the largest bowl was offered in open stock and also in red.
It started in 1957 at Chicago’s most famous nightclub, Chez Paree.
The man known as “the greatest entertainer in the world” was onstage, the smoke from his cigarette trellising the air.
While technically a trademark, it is most often seen referred to as a backstamp. The configuration of the backstamp would undergo a few revisions after the introduction of opal glass kitchenware in 1945. A listing of patterns by year of introduction can be found .
Being embossed rather than incised, and the material being glass, it is obviously molded in rather than stamped. The following are general representations of the various backstamps, which may not look exactly the same on all shapes. Promotional patterns may have been available for as little as a holiday season or a year, standard patterns from two years to as long as a decade in a few instances.