Lambretta tail light lens screw for series 1 and early series 2Two are required to hold the lens in place.
The Complete Spanner's Manual: Lambretta Scooters by Martin 'Sticky' Round (Author) Third Edition
The Unofficial Lambretta Manual Update by Mark Haines
LAMBRETTA - ILLUSTRATED GUIDE TO THE IDENTIFICATION by Vittorio Tessera
Lambretta Performance Tuning and Conversions - 8099990