No, he came back to the US in 1971 and didn't return ( though he may have gone there on his college trip ). It is not the "permanent address" that determines from where the card is issued. It is the mailing address. Even if he had a permanent address in Indonesia, does it make any sense to have your card sent there instead of having it mailed to where you are living ?
How do you know the only office for processing such applications was in Baltimore ? Do you have documents from the SSA dating to 1976-77 to back that up?
From Social Security website:
Since 1972, when SSA began assigning SSNs and issuing cards centrally from Baltimore, the area number assigned has been based on the ZIP code in the mailing address provided on the application for the original Social Security card.
Well, I’ve also read that he visited his mother in Indonesia some summers growing up. And that would have been his permanent address, since that’s where his parents lived.
If there was actually an Indonesian refugee office in Connecticut processing apps for foreigners, as another poster asserted; that’s the address that would have been on the paperwork that was sent to Baltimore.