5310-00-226-0264 (FV558)
NSN 5310-00-226-0264 (NIIN 00-226-0264) is a flat washer in Federal Supply Class 5310, Nuts And Washers — a washer having a centrally located hole with a solid or laminated cross-section and two flat parallel bearing surfaces. Manufacturer part number FV558 (Saeco, CAGE 98817).
Key specs: 75 to 105.5 rockwell b hardness; full characteristics table below. NIIN assigned January 1961; DEMIL A (none required).