A plain nut on which has been assembled a nonremovable washer.
NSN 6135-01-383-0151
NSN 5935-01-024-5606
NSN 5915-00-261-9970
NSN 5930-01-263-7981
NSN 5905-00-603-7155
NSN 6240-01-275-4535
NSN 5915-01-633-9845
NSN 5998-00-413-6506
NSN 5965-01-519-8228
NSN 5915-00-416-3823
NSN 5925-01-024-9568
NSN 6320-01-171-3238