Found something (I guess). Here some info on +GF+ BB:
http://www.velocipedesalon.com/forum/f2/cinelli-lugs-19760-4.html
http://www.cinelliregistry.com/ - 4 bikes with +GF+ BB
and
http://www.swissbicycles.com/allegro...tory-pre-1940/
If it is
Georg Fischer BB then those other marks "818" might be the year and month of production.