Dell mapback front & back: "The Man in Lower 10"

• Title: The Man in Lower 10 (though the pedantic side of me must note that most references and the title page of this book list it as The Man in Lower Ten)
• Author: Mary Roberts Rinehart (1876-1958). She was a Pennsylvania native who had a successful and pioneering career as a mystery writer. She had sold more than 10 million books at the time of her death. I call her pioneering because, as Wikipedia notes, she "is considered the source of the phrase 'The butler did it' from her novel The Door (1930) ... (and) is also considered to have invented the 'Had-I-But-Known' school of mystery writing."
• Cover artist: I'm not sure. It might be out there, but I couldn't find it on Bookscans.com, J. Kingston Pierce's great piece on CrimeReads, or Mystery Scene. Answers or hot leads welcome!
• Mapback artist: Again, I'm not sure. But it could be Ruth Belew, who did at least 25% of the mapbacks. On CrimeReads, Pierce writes:
  

  "Certainly the best-remembered of Dell's mapmakers is Ruth Belew, a rare women laboring within the male fraternity of mid-20th-century paperback designers. Biographical information about Belew is sparse, but she was evidently a Chicago illustrator, who — working from clues and descriptions in each book’s narrative — rendered her crime scenes on cardboard, at twice the finished paperback dimensions. She often added nifty identification banners and numbered 'keys' to help readers locate rooms or landmarks integral to the plot. Dell editors double-checked the accuracy of her drafts, requested any necessary changes, and then sent them to lithographic colorists who’d fill her compositions with arresting hues."

• Publisher: Dell Publishing Company
• Publication year: This is 1937 edition of a novel first published in 1909. Per the cover, this is No. 124 in the Dell series. The novel was later reprinted by Dell, with a different cover, as No. 403.
• Original price: None listed.
• Pages: 240
• Format: Paperback
• First sentence: McKnight is gradually taking over the criminal end of the business.
• Last sentence: "Say," he called, in a hoarse whisper, "shall I throw the key down the elevator shaft?"
• Random sentence from middle: Richey's flippancy is often a cloak for deeper feeling.
• Best character name in novel: Budd Wilson Hotchkiss
• Goodreads rating: 3.57 stars (out of 5.0)
• Goodreads review excerpt: In 2012, Janiece wrote: "The style of writing is interesting and the setting of the 1920s takes me back to a time when train travel was the norm. Being a fan of Mary Roberts Rinehart since childhood, I am re-reading her books now and see much more in them that I didn't get before. Solving mysteries is more about inductive reasoning and observation than high tech diagnostics."
• Amazon rating: 4.1 stars (out of 5.0)
• Amazon review: In 2014, Bratty_me27 wrote: "Is being the main suspect in a murder the right time to fall in love? Read this book and find out."
• Previous mapback post: In 2013, I wrote about Date with Death.