5310-00-537-2652 (19021)
NSN 5310-00-537-2652 (NIIN 00-537-2652) 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 19021 (Franklin Engine Co Inc, CAGE 70188).
Key specs: 85 to 100 rockwell b hardness; full characteristics table below. NIIN assigned January 1963; DEMIL A (none required).