Nos. 482, 570, 883, Dockets 75-4099, 75-4126, 75-4139. Argued February 20, 1976. Decided April 27, 1976. Albert X. Bader, Jr., New York City (Simpson Thacher Bartlett, Martin H. Zuckerman, New York City, and James S. Frank, Brooklyn, N.Y., on the brief), for petitioner American Can Co. James F. Gill, New York City (Robinson, Silverman, Pearce, Aronsohn, Sand Berman, New York City, Peter B. O'Connell, on the brief), for petitioner Local One. David L. Gore, Pittsburgh, Pa. (Bernard Kleiman, Chicago