Yes. that was and still is the common practice today, when making plates. They rest them on holders as they go though the firing kiln, which today is a mechanical process on a belt the goes into the Kiln. Back in the late 19th century and before they would sit the plate on the floor of the kiln. This is a good way to note a plate is older, because where the plate rested on the floor (or shelf) There would be no glaze. This is just a general rule, and not always the case, I have seen a couple of older Blue and whites, that would have some glaze on the plate foot. Other thing to note about older plates is they sometime tend to be out of round or not exactly flat. Again these are general rules, and by no means prove the age.