This is a Corning Ware 4 quart open roaster # A-21-B-N in the Country Cornflower pattern. Country Cornflower was the replacement for the Blue Cornflower line in early 1988. It was discontinued in 1993.
This roaster is in excellent condition and is marked "A-21-B-N 12 1/4" X 10 1/2" X 2 1/2" under one of the handles. It is marked "Corning Ware 89A" under the other handle.
Of the three sizes of roasters that were introduced by Corning Ware in 1976 it is this one (A-21) that has stuck around and become the primary roaster.