A research clue, not yet linked to a specific person. A 1936 New York arrival manifest lists, as a US contact / friend in Paris, “J. Jeannopoulos” at 24 rue Tournefort. The address is in the 5th arrondissement, near the Université Sorbonne.
Whether “J. Jeannopoulos” was Constantine, John Lazare, or an unrelated namesake remains an open question. The Paris address might be a Constantine-era contact, since he was in Italy and Europe through the mid-1930s. Saved here so it’s not lost.