By "keel", I understand the material at the muzzle that fills in the gaps where the barrels and ribs come together. I don't have an original Ithaca to look at close at hand, but Walt and Steve, are you saying that there are gaps under the top and bottom ribs at the muzzle? Walt, looking at the middle photo in your book, P. 317, that Flues appears to me to have keels, or what I think of as keels.