A plain nut on which has been assembled a nonremovable washer.
NSN 5996-01-435-2766
NSN 2925-00-326-6081
NSN 6130-01-504-4152
NSN 5835-00-247-0161
NSN 5965-01-109-2917
NSN 6130-01-448-6393
NSN 5960-00-185-9974
NSN 5920-01-131-6436
NSN 6610-00-515-6462
NSN 6135-01-370-2599
NSN 5999-01-266-0862
NSN 6320-00-476-6898