According to Wikipedia, Fire-King "was originally produced in the 1940s for everyday use, rather than display. It was often sold in bags of flour as a promotional item or was given away at gas stations. Fire-King could also be purchased at local grocery and hardware stores.
Today, Fire-King is an affordable collectible found in antique stores, garage sales, flea markets, and thrift stores, as well as on the Internet."
I recently found a piece of Fire King at a thrift store and have made it into a Chalkboard Plate by painting the middle with several layers of chalkboard paint. It's for sale on my website along with other vintage plates.
This oval platter is a piece of white milk glass in the common Shell pattern. Based on the backstamp on the rear, I have estimated that it dates from 1970.