This "Lambretta Concessionaires" brass legshield badge was fit to most early Lambretta scooters by the British Lambretta Concessionaires.
The Complete Spanner's Manual: Lambretta Scooters by Martin 'Sticky' Round Third Edition 8100072
The Unofficial Lambretta Manual Update by Mark Haines
LAMBRETTA - ILLUSTRATED GUIDE TO THE IDENTIFICATION by Vittorio Tessera
Lambretta Performance Tuning and Conversions - 8099990