Does "they were not of use or to reassure her that they were" mean...

Does "they were not of use or to reassure her that they were" mean "they were not of use or to reassure her that they were useful/of use"?

Context:

Titanic[http://en.wikipedia.org/w/index.php?title=John_Jacob_Astor_IV&action=edit§ion=5]

While traveling, Madeleine became pregnant, and wanting the child born in the U.S., the Astors boarded the RMS Titanic on her maiden voyage to New York. They embarked in http://en.wikipedia.org/wiki/Cherbourg, France, in first class and were the wealthiest passengers aboard. Accompanying the Astors were Astor's valet, Victor Robbins; Madeleine's maid, Rosalie Bidois, and her nurse, Caroline Louise Endres. They also took their pet http://en.wikipedia.org/wiki/Airedale_Terrier, Kitty. The Astors were deeply fond of their dog and had come close to losing her on a previous trip when she went missing in Egypt. Kitty did not survive the sinking.^[15][16] A short while after the Titanic hit the iceberg that caused her to sink, Astor informed his wife of the collision, but told her that the damage did not appear to be serious. Some time later as the ship's lifeboats for first class were being manned, Colonel Astor remained unperturbed; he and his family played with the mechanical horses in the gymnasium. At some point Astor is thought to have sliced the lining of an extra lifebelt with a pen knife to show his wife its contents, either to prove that they were not of use or to reassure her that they were.