A plain nut on which has been assembled a nonremovable washer.
NSN 5895-01-377-3308
NSN 5835-00-987-9341
NSN 5920-00-669-8538
NSN 6240-00-146-9322
NSN 7035-01-535-1450
NSN 6320-00-476-6898
NSN 2925-00-704-3690
NSN 6150-01-427-3764
NSN 5925-01-205-7482
NSN 5835-01-126-9358
NSN 5996-01-416-1489
NSN 6150-01-139-3158