Cup washers are used where perhaps a pan head screw would be better but a cup washer is better at spreading a load. They were fitted on most Lambrettas on the legshields.
Grease nipples are designed for use in conjunction with a grease gun to lubricate whatever they are attached to - they are hollow so the grease goes down inside them. As time went on Lambrettas had less and less grease nipples but every Lambretta needs some.