The 3 rivet {which are actually stop pins} are present on both clutches. The 16 rivets hold the individual 8 segments to the adapter plate, the clutch on the left is a monodisc driven plate with all 8 cushion ramps made out of one piece and is more expensive in tooling but quicker make especially assemble. They still have the same facing rivets that hold the facing to the segments or mono disc and they still have the same 3 stop pins holding the disc adapter and retaining plate together
Most of our monodisc tooling is now in the bin as production runs are too short. Most driven plates that were OE by ourselves are either made in Italy or India depending on the part number.
Ps the stop pins have 2 roles, one ,to hold the whole assembly together and two, to stop the rotation once the springs reach their design load.
I made a couple of plates for my Herald myself before the tooling was shipped out.