In NLRB v. Signal Oil Gas Co., 303 F.2d 785 (5th Cir. 1962), this Circuit has discussed at length the obligation of the employer where there are competing unions and "the situation [has] not crystallized," not to exert influence thereby tipping the scales and "depriving the employees of their right to select their representative in a free contest between the rival organizations."
In N.L.R.B. v. National Seal Corp., 2 Cir., 127 F.2d 776, 779, Judge Learned Hand very definitely interpreted a rule having to do with union membership.