5310-00-042-6217 (426217)
NSN 5310-00-042-6217 (NIIN 00-042-6217) is a lock washer in Federal Supply Class 5310, Nuts And Washers — a washer, usually round, with a centrally-located hole. Manufacturer part number 426217 (Army Weapons Command Attn, CAGE 21450); also referenced as FFW84CLASSASTYLE2 (Federal Specifications Promulgated).
Key specs: 45 to 53 rockwell c hardness; full characteristics table below. NIIN assigned January 1963; DEMIL A (none required). Related NSN 5310-00-836-2458.