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I'm paring down and was taking pictures and noticed something odd. I have two of the 2.5 quart casserole dishes with lids. They are marked the same on the bottom and came from the same home along with all the other casserole dishes and pie plates. All have the same 1967-1969 stamp on the bottom. However--the lids, though on the same casserole, are very different. The one seems to have an optical pattern in the glass. It was very hard to photograph, but this lid has a ripple effect that creates a refracted light pattern on the bottom of the dish. There are also very light indentations-four on each side (or more aptly,one on each corner and two in between on each side. It is also numbered differently. The other lid is marked "A 9 C'. This lid is marked "A-9-C" and on the opposite side a number 12. The other lid has no 12-even though they are the same size and come from the same date/home/set.
I've spent hours trying to find anything else like it but have found nothing. I kind of don't want to part with them now. Anyone have any info?