In 1935, the Mickey Mouse lunchbox was produced, and children went wild. By the 1950's, pretty much every popular character, musical group, television show, etc., had a lunchbox and at the time it was one of the more exciting things for children to shop for.
The boom of steel lunch pails stopped around 1987 with Rambo being the last character produced. It phased out for several reasons including the much higher cost for it versus plastic or vinyl alternatives.
The colorful lunch pail below is from the 1880's.