Crown nut these are nuts that are used on various types of axles and shafts, where there are vibration and dynamic loads. Holes are drilled in these axles, in which, after tightening the nut, cotter pins are inserted, which in turn pass through the vertical slots in the nut. This allows you to securely lock the nut and prevents it from unscrewing when vibrating.
Scope DIN 979 is used in mechanical engineering, construction.
Material stainless steel. The grade of steel A2 allows to use fastenings at considerable differences of temperature and in the aggressive and humid environment.
No coating.
Analogs GOST 5932-73. GOST 5919-73. ISO 7038