My grandfather immigrated to the U.S. in 1928 from Italy (I have his passenger manifest). In late 1937, after he became an American citizen and gained a U.S. passport, he took a trip back to Italy to visit his ailing mother, and returned to the U.S. in April 1938 (I have this return manifest, as well). My question is, would a passenger manifest exist that documented my grandfather's trip from the U.S. to Italy in 1937? We have documentation from the Italian Consulate in Pittsburgh absolving him of Italian military duty for a period of 12 months starting with his trip back to Italy in 1937. The document mentions the ship and date (Conte di Savoia, November 20, 1937, sailing from New York to Naples), but for a family history project we would like to prove he was in fact on this ship.
As an aside, it seems that while my grandfather gained citizenship through his father (he was 17 in 1928 when he joined his father in the U.S. who was naturalized the year before), he was sufficiently concerned that at least the Italian authorities in 1937 would consider him at the least a dual citizen.