I recently almost lost the C-spanner thats used for adjusting the pre-load on the rear shock absorbers. Left side was easy but right side was behind the exhaust. Fortunately I found the tool-kit C-spanner and the day was saved as it has the needed 90 degree angle at the grip.
I figure others might benefit from a quick note on this incase they DID loose theirs and need to adjust the pre-load on the right side. Without this tool you would have to remove the entire exhaust assembly just to get enough leverage to adjust the right-side shock pre-load.
This is the Parts Piaggio code for the tool-kit which includes the C Spanner that has a 90 degree angle at the gripper end to fit up between the pre-load and the exhaust. https://www.parts-piaggio.com/gilera-piaggio-vespa/assignment_spare_parts/651193
Easy Parts is probably the best source and is a trusted reliable vendor. https://www.easyparts.nl/Complete-Tool-Kit-p33588323
You can also buy it at Scooter Center (sorry for long URL)
Lef side is easy and can be done with Channel Locks (though those tear up the metal a bit) or you can get any Square Nose 1 1/4"-3"(32-76) C Spanner. But that can only be done for the left side, the right side needs specialized C Spanner or allot of parts have to come off.