We're suckers for anything to do with Sherlock Holmes, after all, London is sweeter for his presence. We even watched that cartoon which had him thawed out and solving crimes on the moon.
Eleven countries have produced fourteen Sherlock Holmes-related postal offerings, beginning in 1972 with Nicaragua's 50th Anniversary of Interpol issue,"The Twelve Most Famous Fictional Detectives," in which Holmes was on the high value, and continuing through the 2000 South Africa writers stamp with Sir Arthur Conan Doyle.
Good stuff! And there's plenty of Holmesian eye candy to help kill a slow Monday morning. All of which makes a nice appetiser for the aptly named A Study in Sherlock.