Now that I've looked at my bike and the type IV photo I see a few very minor details are different. For example the headlight shell is different, it doesn't have a speedometer and the speedo drive from the rear hub isn't there. These could be running repairs (bodges) over the last 60 years or maybe they made a few examples for trials to a slightly different spec.

I have requested documents through the Moto Guzzi archive service, though I think that is mostly aimed at more recent models.

"this means the end of the horse-drawn Zeppelin!" - N Seagoon