5310-01-193-7654 (FF-W-84)
NSN 5310-01-193-7654 (NIIN 01-193-7654) is a lock washer in Federal Supply Class 5310, Nuts And Washers — a washer, usually round, with a centrally-located hole. Manufacturer part number FF-W-84 (Federal Specifications Promulgated, CAGE 81348); also referenced as MS35338-145B (National Aerospace Standards).
Key specs: 35 to 43 rockwell c hardness; full characteristics table below. NIIN assigned November 1984; DEMIL A (none required); unit of issue EA (each), $0.81 gov standard price; ships at 0.02 lb / 0.0001 cu ft.