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 6145-01-601-3902
NSN 5935-00-143-1399
NSN 5999-00-518-1007
NSN 5920-01-414-6983
NSN 5895-00-644-5712
NSN 6105-00-639-6857
NSN 5835-01-147-7526
NSN 6135-01-175-4589
NSN 5935-01-607-0883
NSN 6105-00-962-9003
NSN 6240-01-581-2944
NSN 5999-01-304-4367