5310-00-252-9138 (34-270)
NSN 5310-00-252-9138 (NIIN 00-252-9138) 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 34-270 (Bae Systems Information And, CAGE 81413); also referenced as 57-1158 (Seeburg Corp The Seeburg Products).
Key specs: 55 to 60 durometer hardness; full characteristics table below. NIIN assigned January 1963; DEMIL A (none required); export Schedule B 4016.93.0000.