Vintage Corning Ware Double Boiler Insert P-17-B Cornflower Blue NO LID
Good condition with a few light utensil marks here and there.
It is a double boiler insert and fits inside a P - 2 1/2 - B
About 8 5/8" wide and just over 3 1/4" high.
Made in the 1960's.
Please check the photos for the best idea.