A plain nut on which has been assembled a nonremovable washer.
NSN 5905-01-233-3213
NSN 5975-01-363-4171
NSN 6645-01-085-8879
NSN 6650-00-296-4670
NSN 5950-01-198-2533
NSN 6610-01-484-8980
NSN 5999-00-659-3874
NSN 5895-01-026-7387
NSN 5996-01-437-6227
NSN 5935-01-352-5470
NSN 5930-00-518-1492
NSN 7035-01-211-5636