The Baker Street Irregulars is a literary society dedicated to the study of Sherlock Holmes, Dr. Watson, Sir Arthur Conan Doyle, and the Victorian world. It is the oldest existing Sherlockian society in the world. Founded by Christopher Morley and others at the Hotel Duane, New York City.
At Amateur Mendicant Society we read that the: "Amateur Mendicant Society of Detroit Established 1946 -- A Scion of the Baker Street Irregulars" and they lay claim to having erected the plaque at Barts.
The Criterion plaque was erected by the Inverness Capers of Akron, Ohio, who we imagine as another "scion" of the Baker Street Irregulars.