Don Foster had found a copy of an 1844 letter from the Troy Sentinel publisher, Norman Tuttle, to Clement Clarke Moore in the
New York Historical Society. The letter was answering a question of Moore's that, from context, asked
whether Tuttle had known when Tuttle published the poem just who the author was. Tuttle's answer was that he had not,
but had since heard that the poet was Moore.
Don thought of this as "the coast is clear" letter, giving Moore the information that if he took credit
for the poem, the Troy Sentinel people weren't going to come forward and bite him in some inappropriate place
with the name of the real author.