“The Adventure of Charles Augustus Milverton” ends with a description of “a shop window filled with photographs of the celebrities and beauties of the day”.
So what kind of “shop” is this? A photography studio? A souvenir store? A department store?
Here’s the complete quote: (last paragraph of the story, link below)
Holmes had not said one word to me about the tragedy which we had witnessed, but I observed all the morning that he was in his most thoughtful mood, and he gave me the impression, from his vacant eyes and his abstracted manner, of a man who is striving to recall something to his memory. We were in the middle of our lunch, when he suddenly sprang to his feet. “By Jove, Watson, I’ve got it!” he cried. “Take your hat! Come with me!” He hurried at his top speed down Baker Street and along Oxford Street, until we had almost reached Regent Circus. Here, on the left hand, there stands a shop window filled with photographs of the celebrities and beauties of the day. Holmes’ eyes fixed themselves upon one of them, and following his gaze I saw the picture of a regal and stately lady in Court dress, with a high diamond tiara upon her noble head. I looked at that delicately curved nose, at the marked eyebrows, at the straight mouth, and the strong little chin beneath it. Then I caught my breath as I read the time-honoured title of the great nobleman and statesman whose wife she had been. My eyes met those of Holmes, and he put his finger to his lips as we turned away from the window.
https://en.wikisource.org/wiki/The_Return_of_Sherlock_Holmes/Chapter_7