A plain nut on which has been assembled a nonremovable washer.
NSN 5835-00-213-9811
NSN 6130-00-081-4103
NSN 7035-01-123-8723
NSN 5996-01-522-1695
NSN 5996-00-084-8940
NSN 5985-00-087-4317
NSN 6135-00-152-8729
NSN 2925-00-587-8968
NSN 5960-01-173-7956
NSN 5990-01-219-9018
NSN 5998-01-250-3265
NSN 5895-00-185-4543