Serena Pottery USA Dishes Pattern 613

Here is a very interesting and versatile piece of USA pottery, by Serena. The item number is 613. There are two pieces, and as seen in the second photo, I believe it is made to be a covered dish. The bottom of the tallest piece is the only one marked, for one. The bottom piece has a flat edge rim and the shorter piece has a recessed rim, so they fit together nicely, but not perfectly tight. They could, however be used separately as serving dishes. It could be a "refrigerator dish". They are off white or ivory in color. The "bottom" is 11" long, 6-3/4" wide and 3-1/2" deep. The "top" is 11-1/4" long, 7" wide and 2" deep. This set is in excellent condition with only expected wear issues. Probably from the 60's. Does not say "oven-proof" so I wouldn't recommend trying to use them for baking a casserole!