5310-01-059-0991 (3K8909)
NSN 5310-01-059-0991 (NIIN 01-059-0991) is a lock washer in Federal Supply Class 5310, Nuts And Washers — a washer, usually round, with a centrally-located hole. Manufacturer part number 3K8909 (Caterpillar Inc, CAGE 11083).
NIIN assigned April 1978; DEMIL A (none required).