Thanks for info David. A friend had a military Bianchi single. It had a very low "marching" gear normally locked out but for parades.
Regarding electrics I remember seeing a wiring diagram for a Stornello. The normal three phase alternator used each raw phase individually. One provided spark via coil (possibly with redundant spark), a second with single phase rectification charged battery and a third provided AC headlight supply. Kept costs down I guess.
ETA: just checked my Italian hard back Colombo book which is possibly earlier than yours, printed around 1977 and running only to 343 pages. Cannot find any mention of your bike in it unfortunately.
As mentioned earlier the engine shape is nearest to a Lodola (1956-66) which came with 175cc ohc engine or pushrod 235cc, I had both. Wonder which valve operation yours has?
It has the same general layout as Loyola but is much more chunky, a lot of people have assumed it's a 500. I looked at the various Lodolas and Stornellos when I was trying to work out what it was but none of them looked the same. One of the
earlier prototypess has an odd cable operated lever on the cases, which I had thought might be a parade/marching gear.
Mine has pushrods and a dynamo, the lights are much brighter having given it a good run on Sunday. The sparks come from a low tension mag with a coil under the tank.
The Bianchi won the contract that mine lost. It too seems to be a pretty odd machine. Sometimes the requirements lead in the wrong direction, that's why you have to challenge them and work with the customer to work out what they really need.