That's not an original rivet.Paul,
Sigma MC 10, around € 25,00, will tell you when to fill up.
Easy to install, no changes on your SFC, reliable and accurate.
HTH
Gerald
Since France has now brought in a control, aka TÜV or MOT, I don't know how I'll get the SFC through it apart from bribery.
Apart from details like a speedo, SFCs were never homologated in France and all sold new with SF documents where the numbers don't correspond to the bike.
Fun.
Paul