Corning Ware loaf pan from Corning Glass's Blue Cornflower series, sold from 1958-1988. This is the original Corning Ware Pyroceram glass and ceramic material that can go from freezer to oven to table top.
This dish measures 7" x 5-1/2" x 3", holds 1-1/2 quarts, and is marked P-4-B on the bottom, though it is hard to see. It is in very good shape with little wear but does have some usage marks on the inside bottom and handles.