Place the knuckle, marrow bones, and optional calves foot into a very large pot with vinegar and cover with water. Let stand for one hour. Meanwhile, place the meaty bones in a roasting pan and brown at 350 degrees in the oven. When well browned, add to the pot along with the vegetables. Pour the fat out of the roasting pan, add cold water to the pan, set over a high flame and bring to a boil, stirring with a wooden spoon to loosen up coagulated juices. Add this liquid to the pot. Add additional water, if necessary, to cover the bones; but the liquid should come no higher than within one inch of the rim of the pot, as the volume expands slightly during cooking. Bring to a boil. A large amount of scum will come to the top, and it is important to remove this with a spoon. After you have skimmed, reduce heat and add thyme and crushed peppercorns.