Nut - nylon stop 6-32 black oxide
6-32 nylon insert lock nut or esn (elastic stop nut) in black oxide finish.
Black-oxide 18-8 stainless steel nylon-insert locknut with 6-32 thread size is 5/16 inch wide x 11/64 inch high.
Used to secure ring and rod and other high vibration mechanical assemblies in Williams. Bally, and Stern games.