Surprise witness before NLRB investigation. Washington, D.C., Dec. 14. Mary Moore, employed in the National Labor Relations Board Office in Boston, was a surprise witness today before the House Committee Investigating the NLRB. To determine whether the Board is 'conducting a company union,' the committee asked Miss Moore to identify letters she wrote when she was in Washington and was serving as Regional Correspondent of the NLRB Employees' Union. One of the letters Miss wrote was on Board stationary