A plain nut on which has been assembled a nonremovable washer.
NSN 5998-00-845-4272
NSN 5965-00-990-8669
NSN 5975-01-606-9379
NSN 5835-01-370-4292
NSN 6650-00-578-6543
NSN 7035-00-870-0290
NSN 5915-01-118-0386
NSN 5998-00-244-8629
NSN 6610-00-264-0961
NSN 5998-00-661-0380
NSN 5930-01-534-7835
NSN 5855-00-821-7512