Catalog calls this: metric spring - din 127b lock washer
A washer which is usually round with a centrally located hole. Its edges and two bearing surfaces are so designed that applied pressure brings into play the spring tension and/or frictional locking principle which materially resists any tendency toward turning. It may be made of one or two pieces
Classification: Spring washers and other lock washers, iron or steel
NSN 5945-00-813-5138
NSN 6110-01-541-8076
NSN 5950-01-250-1559
NSN 5998-00-055-8537
NSN 6110-01-373-1587
NSN 5950-01-463-2796
NSN 6130-01-308-3227
NSN 6620-00-231-9227
NSN 6240-01-054-2289
NSN 6150-01-605-3392
NSN 5935-00-269-3676
NSN 7035-01-601-0160