FB is Fratelli Brivio, makers of hubs and cranks. Much of their production was done for others. Hubs made under a great many different names.

Fb Hubs

A variety of their hubs are illustrated in this forum thread:

http://www.bikeforums.net/classic-vi...os-needed.html

Somewhat doubt those on your cycle are FB as they have five-piece bodies. FB bodies are usually three-piece. Two possible makers are Agrati and Gnutti but there are others as well.