On this parts fiche the Nut,flange,6mm is the most specified component.
Some items from this specific schematic: Bag,service Book, Seat Assy,single (jdm), Nut,flange,6mm, Lether Comp,seat (jdm).
The most reasonably priced component used on the Nh50m 1992 (n) Japan Af20-110 / Type 2 F-12 is the Nut,flange,6mm.