A plain nut on which has been assembled a nonremovable washer.
NSN 5965-01-562-5830
NSN 5996-01-332-6988
NSN 6110-01-321-1276
NSN 6610-00-149-1534
NSN 5950-01-441-1155
NSN 6610-00-087-2434
NSN 6110-00-724-3136
NSN 6150-00-148-8515
NSN 5990-01-363-3370
NSN 6610-01-535-8757
NSN 6320-01-381-7023
NSN 5990-00-212-4316