Thanks, you got it right. 1970 is the birth year and father lived in the United States for decades prior but had a child while out of the country, the naturalized citizen. The question is really about whether natural born citizenship is available to children of an American citizen when the child is born abroad, but the parent was deceased before majority age. Naturalization would probably be sufficient, but given that even naturalization is theoretically at risk, maybe obtaining outright natural born status is better insurance. There is an N-form for this sort of thing.