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Original bar would have been 3TTT Gran Prix. Centre section of bar and clamp of stem are 26.0mm size.
If drive chain which came with cycle is Everest brand it is likely original.
Currently thinking 1963-67 for a date window.
It appears there is no lubrication port on the bottom bracket shell. Is this correct?
If you have not done so already you may wish to visit the Condorino web site. It is mainly about the Legnano badge but has some information on other Bozzi badges as well. It gets into parts suppliers employed by the manufacturer and shows fittings examples from different eras.
https://condorino.com/
3TTT Gran Prix entries at
VB -
http://velobase.com/ViewComponent.as...m=102&AbsPos=0
http://velobase.com/ViewComponent.as...=112&AbsPos=18
http://velobase.com/ViewComponent.as...=112&AbsPos=19
On quality model bicycles Bozzi employed Ambrosio Champion stems and bars through ~1962, 3TTT Gran Prix ~1963-70, first generation Record ~1971-73 & second generation Record beginning ~1974.
Hope this helps you a bit.
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