(Source: A Day by Day Chronology of Mr. Sherlock Holmes according to Zeisler and Christ, compiled by William S Dorn.)
July 19, 1889: Holmes returned the missing letter to Trelawney Hope’s dispatch box. [SECO]
Holmes raised the lady. “I am thankful, madam, that you have come to your senses even at this last moment! There is not an instant to lose. Where is the letter?”
She darted across to a writing-desk, unlocked it, and drew out a long blue envelope.
“Here it is, Mr. Holmes. Would to heaven I had never seen it!”
“How can we return it?’ Holmes muttered. “Quick, quick, we must think of some way! Where is the despatch-box?”
“Still in his bedroom.”
“What a stroke of luck! Quick, madam, bring it here.”
A moment later she had appeared with a red flat box in her hand.
“How did you open it before? You have a duplicate key? Yes, of course you have. Open it!”
From out of her bosom Lady Hilda had drawn a small key. The box flew open. It was stuffed with papers. Holmes thrust the blue envelope deep down into the heart of them, between the leaves of some other document. The box was shut, locked, and returned to his bedroom.
July 19, 1898: The first Dancing Men appeared. [DANC]
Holmes held up the paper so that the sunlight shone full upon it. It was a page torn from a notebook. The markings were done in pencil, and ran in this way: –