No. 88-3141. Argued September 15, 1988. Decided January 4, 1989. David M. Silberman (argued), Laurence Gold, Washington, D.C., Miriam L. Gafni, Freedman and Lorry, P.C., Philadelphia, Pa., for petitioner. Peter Winkler (argued), Michael D. Fox, Aileen A. Armstrong, Rosemary M. Collyer, John E. Higgins, Jr., Robert E. Allen, N.L.R.B., Washington, D.C., for respondent. Lawrence B. Fine (argued), Julia W. Manning, Morgan, Lewis Bockius, Philadelphia, Pa., for intervenor. Petition for review from the