Vintage Corningware Summer Blush Casserole Dish A-2-B 2L With Glass Lid

Good vintage condition. Minor signs of wear shown in pics. Please look at all pics and zoom in for a closer view. Close ups highlight flaws. The discolouration on the inside, I’m not sure what it is. I’ve tried soap and water, barkeepers friend and a magic eraser to get it off and it’s not coming off. The mark has no texture. Measurements in pics. No chips or cracks. Vintage Corningware Summer Blush Casserole Dish A-2-B 2L With Glass Lid 215US