Season the veal scallops with pepper,then dip them in flour and shake off excess.In a heavy skillet,melt margarine with olive oil over moderate heat.When foam subsides,add veal scallops four or five at a time,and saute them until golden brown. Transfer the veal scallops to a plate.Pour off most of the fat from the skillet,leaving a thin film on the bottom.Add half cups beef stock and let boil briskly for a few minutes,stirring constantly. Scrape in any browned bits clinging to the bottom and sides of the pan. Return the veal to the skillet and arrange lemon slices on top. Cover skillet and simmer over low heat for 10 to 15 minutes or until veal is tender when pierced with a knife. Transfer scallops to a heated platter and surround with lemon slices. Add the quarter cup of remaining beef stock to the juices in the skillet and oil briskly until stock turns to a syrupy glaze.Add the lemon juice and cook,stirring,for 1 minute.Pour sauce over scallops. Serves 6. Note: Veal cubes (stewing meat) may be substituted. Pound as flat as possible. Follow directions above,but cooking time will be increased to 45 minutes to an hour over low heat or until tender.