Tales from a Rolltop Desk by Christopher Morley. From the opening short story, The Prize Package:
Published in 1921, this story made me roar with laughter.
I’d never heard of the author before but I should have! From Wikipedia:
Out of enthusiasm for the Sherlock Holmes stories, he helped found The Baker Street Irregulars and wrote the introduction to the standard omnibus edition of The Complete Sherlock Holmes.