Considering the absence of utensil marks and no smoothed down areas of the underside, this skillet appears to be unused or VERY lightly used. There is a nicely centered downward bow (pic with red straightedge) which I have found to be common with this size, so you can't place it on all the elements of your glass top and use it.Don't think someone would do that anyways. One layer organic flaxseed oil.
Check all the pics and ask any questions you may have. The item "Griswold 20 Cast Iron Skillet" is in sale since Wednesday, December 21, 2016. This item is in the category "Collectibles\Kitchen & Home\Kitchenware\Cookware\Cast Iron". The seller is "fruitbasketmaniac" and is located in Knoxville, Tennessee. This item can be shipped to United States.