Lambretta steering lock aluminum covering disc This is a Welsh plug to cover the steering lock mechanism in the headset bottom.
INNOCENTI 15088003See fig. 38 in the image below.
The Unofficial Lambretta Manual Update by Mark Haines
LAMBRETTA - ILLUSTRATED GUIDE TO THE IDENTIFICATION by Vittorio Tessera
Lambretta Performance Tuning and Conversions - 8099990
Lambretta Tuning Manual by Dave Webster - 8099992