Picked this up the other day, along with a Wagner Ware center logo, another Dutch oven, and a no 4 Lodge 3 notch. Interesting in that the lid is a slant and the base is a block. I know patent dates don't mean much, but the dates on these two pieces are only a month apart and the owner swore it was purchased new by her grandmother. Did Griswold ever mix and match during the switch over, or did the owner just mix the lids in the deep dark past? I've seen a few others listed on ebay this way (slant lid with block base), but it's rare.
