No. 19875. June 10, 1970. Guy Farmer, Washington, D.C., for petitioner; John A. McGuinn, Patterson, Belknap, Farmer Shibley, Washington, D.C., Nicholas R. Criss, Jr., Hugh M. Finneran, PPG Industries, Inc., Pittsburgh, Pa., on the brief. Nancy M. Sherman, National Labor Relations Board, Washington, D.C., for respondent; Arnold Ordman, Gen. Counsel, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, Hans J. Lehmann, Atty., National Labor Relations Board, Washington