It recently dawned on me that the curator of the Nemirovsky Exhibit at the Museum of Jewish Heritage in New York City may have more information to share about what writing implements were in the exhibited valise.
I called her on Monday, and she returned my call the following day.
While she doesn't know the answer, she is fluent in French, and believes some reference was made to Ms. Nemirovsky's fountain pen and/or the ink in a French language biography. At her convenience, she agreed to check and get back to me.
She did mention during our conversation that when she examined the valise she noticed it was ink stained--aqua.
An answer may be forthcoming.