Lambretta series 3 CEV type bulb holder "clip" (for headlamp glass to bulb holder)See fig. 18 in the image below.
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