Hello Gianandrea,
Thanks for the research.There is much to ponder there. I'd gone with the 5.59 for the id of the machine as it seemed plausible according to the timeframe. Having received your answer I've been undertaking some image searches and found this link to a S.16 at Guidonia in 1944 ! surrounded by Australian troops:
https://www.alamy.com/130-siai-s16-a...ip%3d0%26pl%3d
I would never even have thought about any S.16 variant surviving to this date,never mind seeing photos of two.
Thanks also for the information on the use of the CMASA G.8 in use as staff aircraft which is very informative and helpful.
Regards,
Clint