Chuck you will also find that the BB shells and axle are also dated, you are the proud owner of a pre P-R P-R Bianchi! I have 2 P-R mechs and the one without P-R on it def seems the rarer (they were still importing Bianchis into the UK with the PR mech in 1959) - or at least thats what we can make out amongst the Bianchi owners in the UK/VCC.
Also for sake of argument all of the models we know of all have slightly different detailing - eg some wheels have early mark one slab sided small flange camapag hubs with solid axles, some with FB with no detailing some with FB with the dimple and some with skewers and some with square clamps etc etc, none of us can make our minds up about what went into them definitively
Rgds Mike 87)
in Greenwich and sunny (just about to ride my Sun Manxman to the Tube station to go into work...)