The Washer,plain, 6mm is the cheapest item from this partsfiche.
seventeen components are shown in this Sh50 1984 Great Britain Sh50-500 F-12-1 Seat exploded diagram.
Some items from this specific schematic: Bolt, Flange,6x12, Wrench,box,p21, Washer Plain 7mm, Nut,hex 6mm.