In the Spring 2011 "The Hemingway Review" they have included this topic by Nat Benchley. I received my copy of the "Review" yesterday.
Abstract: In the mid-1930s, the humorist Robert Benchley invited his friend Ernest Hemingway up to his suite at the Royalton Hotel in New York. During the visit, Hemingway wrote lewd or silly inscriptions to Benchley in four of his books: In Our Time, A Farewell to Arms, Green Hills of Africa, and The Fifth Column. Here Benchley's grandson Nat offers up those inscriptions for edification and amusement.
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Robert Benchley, in his essay "Why Does Nobody Collect Me?", which appears, beginning on page 354 of Chips off the Old Benchley, describes Hemingway paying a visit to Benchley's room in New York City, during which the author and adventurer "took a pen in his chubby fist, dipped it in a bottle of bull's blood, and wrote the following:
To Robert ("Garbage Bird") Benchley, hoping that he won't wait for prices to reach the peak [blank]. From his friend, Ernest ("[blank] [blank]") HemingwayThe "Garbage Bird" reference in connection with me was a familiarity he had taken in the past to describe my appearance in the early morning light of Montparnasse on certain occasions. The epithet applied to himself, which was unprintable except in Ulysses, was written deliberately to make it impossible for me to cash in on the book."
Benchley goes on to describe Hemingway's personalization of Mr. Benchley's copy of A Farewell to Arms, in which he "filled in each blank in the text where Scribner's had blushed and put a dash instead of the original word in every case."