This is the Vintage Yellow Pyrex Refrigerator Container that came two to a set in the orange and yellow sets. The entire set is made to be stackable inside the refrigerator. An innovative replacement for all those plastic containers!
If you like pyrex, or would like to learn more, try the blog Pyrex Love.
The yellow container is marked 501 B and is 1 1/2 cups. The lid is 4 1/4″ x 3 1/2″ and the container is 4 1/4″ x 3 1/2″ at the top and tapers to 2 1/2″ x 2″ at the bottom.
The lid is marked 501 C. They are like new!