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thank you for the picture help!
would guess it to be the next model down from the Specialissima since the headset is the proprietary Bianchi one rather than the Bianchi - Campagnolo one
of course it could be a Specialissima which predates the Campagnolo - Bianchi headset
the saddle pillar is a real prize
Campag launched their pillar ~1956 and for the first year or two it was steel
probably worth several times the cost of an alloy example to a collector...
some of the other fittings appear somewhat later than the frame
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