The French Casserole was one of eight special campaign items offered from 1939 to 1942. The French Casserole is fairly rare. Ten years ago a French Casserole is excellent condition was worth about $250-$300. NOTE: 2019 update the price is still about the same or even a little less depending on color. Most of the casserole dishes available are in yellow. With a lid and in good condition they can be found for as little as $100. Without a lid, expect to spend about $40. There are lids available separately for sale if you are missing a lid.
If you have one you want to price, go to ebay and try to look up your dish in the color and condition you have and see what it has been selling for on ebay. Also check to see if someone has it listed on Amazon or Etsy. Lately casserole dishes have been selling for $7.99 to $250. so you have to match what you have to what is selling. Almost all French Casserole dishes are yellow. As of a few years ago only one has been seen in dark blue, and one in light green.
The regular covered casserole was produced in 1936 and continued for several years. Even though it was produced for several years, the vintage casseroles are still not easy to find. Medium green and fifties colors are usually the most valuable. Do not confuse the French casserole with the Art Deco version. They do not look anything alike but the advertisements are not always right, often mixing up the various casserole dishes.
There are several casserole dishes currently on sale for less than $21. Some are vintage casseroles with lids for less than $25! This is the time to buy these collectors items if you can afford to invest in them or would just like to have them to enjoy.