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 5915-00-478-1736
NSN 6685-01-230-3907
NSN 4140-01-612-0215
NSN 5996-01-633-7979
NSN 5998-00-157-6975
NSN 5990-01-234-0789
NSN 6135-00-635-9187
NSN 5855-01-416-5085
NSN 5999-01-200-3828
NSN 5985-01-137-8861
NSN 6110-01-474-4280
NSN 6620-00-303-9947