Can you ID this derailleur?

My starving musician son is going out on a short tour and is looking for a folding bike to use to do Postmates deliveries while he's in various cities. He has his eye on this 1950s? (60s?) Cinzia folder:

https://chicago.craigslist.org/chc/bik/d/cinzia-folding-vintage-bike/6303969369.html

I'm...