It is very interesting what pieces of iron cookware come from foreign countries. Few other places in the world, if any, use similar pans as the US. Years ago in a small Calif. town there was a large warehouse antiques mall full of imported furniture and other antiques. Among them were a ton (well maybe more like 20-30) bundt style cake molds with different patterns, many with porcelain on the inside and/or outside. The other iron cookware that I remember were a lot of pans like you have, again with many or most having porcelain on the inside but not always on the outside. There were nested sets of graduated size pans, maybe three or four different sizes. I would assume that all the iron cookware came from the same country. The Scandanavian countries maybe? Occasionally, in other places, I would see one or several pans like you have. The ribs on the bottom are probably to help them slide into and out of the oven or to keep the bottom off a stovetop or table maybe. Much like a heat rim would work maybe? Nice pieces. I think the smaller sizes would measure about 6 x 8" while the larger sizes might be 10 x 18. This is only a guess since it has been a good 15 or more years since I saw these pans. I don't know what they are called. They remind me of boats and are probably used for oven baking.