The census number painted directly onto the mudguard sides is something that I've only noticed on Canadian Nortons and seems to have begun in the UK around 1943 ish and then transferred to Italy. Bikes in NW Europe seem to have reverted to the fuel tank.
In all probability, it was on both sides of this bike. Here's another link to a Drive-side photo.
http://mikan3.archives.ca/pam/public...202313,3202240
There are often pattern black out masks on eBay UK for the 6 1/2" lamp. Have you spoken to Ian Wright at Ark Motorcycles ? He's likely to know where to find one.