Waiting for a good encyclopedia about the subject (...), I can only have a look at the few sources I have about.
In a long article about Carrozzeria Campana from 'Auto d'Epoca', there are the same info that can be found from your Fuoriserie's books...it seems that the first cars were a Fiat-powered Sport for Sighinolfi and a couple of sports with a Giannini and a BMW engine.
Chassis was built by a mr. Giovanardi. A couple of articles from Ruoteclassiche don't add much. Onorio and Erasmo Campana started in '47 after a long period working for Bacchelli & Bertolini.
Puzzle car seems to be pre-47, was it built for them?