Notecard about Oscar Slater (19 july)
From The Arthur Conan Doyle Encyclopedia

This notecard was written by Arthur Conan Doyle on 19 july [1927~1930], from 15 Buckingham Palace Mansions, S.W.1 (London).
Notecard
Dear Sir
"The Truth about Oscar Slater" will reach you in a day or two. It is a case that calls aloud to Heaven for Justice so I hope you will note it.
- Yours sincerely
- A. Conan Doyle
July 19.