I haven’t checked the others, but someone else could. Basically what you’re looking for in a 1923 publication is:

— No renewal, either of the work itself or any previous version published that year that it derives from. 1923 copyrights should have been renewed in 1950 or 1951.

— First published in the US, or written by Americans. (Many works first published elsewhere are exempt from renewal requirements, though the rules are complex enough that I won’t go into detail here.)

An interested and knowledgeable literary sleuth could track down the necessary information for books of special interest to then, I’d think.

_Whose Body?_ qualifies as US PD because, even though Sayers was British, her novel was published in the US first (the first British edition didn’t come out till some months later.) It was the first appearance of Lord Peter Winsey in print, so there are no earlier publications it was derived from, as might be argued for a later book in a series. And it was not renewed when required. Partly to avoid potential problems, I transcribed from the US first edition (which is now rather rare) rather than an later edition or reprint that might have different content.

Also, one correction on Australia: They’re not life+50 any more, but are in a 20-year freeze like we are as they transition to life+70. (Works by authors who all died before 1955 are fair game there.) But Canada, New Zealand, and a bunch of other countries are still life+50, or were last I checked.

See http://onlinebooks.library.upenn.edu/okbooks.html for more details.

Baroque (1923)
Behind Locked Doors (1923)
Black, White and Brindled (1923) by Eden Phillpotts
Bones of the River (1923) by Edgar Wallace
Captains of Souls (1923) by Edgar Wallace
Cheri-bibi and Cecily aka Missing Men (1923) by Gaston Leroux
Chick (1923) by Edgar Wallace
Children of the Wind (1923) by MP Shiel
Cole, GDH & M – The Brooklyn Murders – (1923)
Contact and Other Stories (1923) by Frances Noyes Hart
Craig Kennedy Listens In (1923) by Arthur Reeve
Days to Remember (1923) by John Buchan
Dorothée, danseuse de corde (1923)
Dr Thorndyke’s Casebook aka The Blue Scarab (1923)
Feathers Left Around (1923)
Hounded Down (1923) by Roy Vickers
Impromptu (1923) by Elliot Paul
Jim Hanvey, Detective (1923) by Octavus Roy Cohen
Jim Maitland (1923)
John Dighton, Mystery Millionaire (1923)
Klondyke Kit’s Revenge (1923) by George Goodchild
La poupée sanglante & La machine à assassiner (1923)
Many Engagements {short stories} (1923) by JS Fletcher
Michael’s Evil Deeds (1923) by E Phillips Oppenheim
Midwinter (1923) by John Buchan
Monsieur Jonquelle (1923) by Melville Davisson Post
More Lives Than One (1923)
Mr Fortune’s Practice (1923) by HC Bailey
Once In A Red Moon (1923) by Joel Townsley Rogers
Secret Service Smith (1923)
Spooky Hollow (1923)
That Fellow Macarthur (1923) by Selwyn Jepson
The Affair at Flower Acres (1923)
The Ambitious Lady (1923) by JS Fletcher
The Astonishing Adventure of Jane Smith (1923) by Patricia Wentworth
The Big Heart (1923)
The Blackguard (1923)
The Books of Bart (1923) by Edgar Wallace
The Brooklyn Murders (1923); by GDH Cole
The Call Box Mystery (1923) by John Ironside
The Cartwright Gardens Murder (1923) by JS Fletcher
The Cat’s Eye (1923) by R Austin Freeman
The Charing Cross Mystery (1923) by JS Fletcher
The Clue of the New Pin (1923) by Edgar Wallace
The Copper Box (1923) by JS Fletcher
The Eyes of Max Carrados (1923) by Ernest Bramah
The Flaming Spectre of Cloome (1923)
The Four Stragglers (1923)
The Green Archer (1923) by Edgar Wallace
The Green Eyes (1923)
The Groote Park Murder (1923) by Freeman Wills Crofts
The House at Waterloo (1923)
The Inevitable Millionaires (1923) by E Phillips Oppenheim
The King’s Red-Haired Girl (1923) by Selwyn Jepson
The Last Secrets {essays and articles} (1923) by John Buchan
The Lone Wolf Returns (1923) by Louis Joseph Vance
The Mazaroff Murder {aka The Mazaroff Mystery} (1923) by JS Fletcher
The Million-Dollar Diamond (1923) by JS Fletcher
The Missing Million (1923) by Edgar Wallace
The Moth-Woman (1923) by Fergus Hume
The Murder on the Links (1923) by Agatha Christie
The Mysterious Chinaman (1923) {aka The Rippling Ruby}
The Mysterious Mr Garland (1923) by Wyndham Martin
The Mystery of Glyn Castle (1923)
The Mystery Road (1923) by E Phillips Oppenheim
The Nature of a Crime (1923), with Ford Madox Ford by Joseph Conrad
The Orange Divan (1923) by Valentine Williams
The Other Story, and Other Stories, (1923) by Henry Kitchell Webster
The Red Redmaynes (1923) by Eden Phillpotts
The Return of Anthony Trent (1923) by Wyndham Martin
The Rover (1923) by Joseph Conrad
The Secret of the Sandhills (1923) by Arthur Gask
The Secret of Thurlestone Towers (1923)
The Seven Conundrums (1923) by E Phillips Oppenheim
The Sinister Mark (1923)
The Step on the Stair (1923) by Anna Katherine Green
The Thing at Their Heels (1923) by Eden Phillpotts
The Valley of Lies (1923) by George Goodchild
The Veiled Prisoner (1923) by Gaston Leroux
The Vengeance of Henry Jarroman (1923) by Roy Vickers
The Whipping Girl (1923) by Ralph Rodd
The Wild Bird (1923) by Hulbert Footner
The Woman Accused (1923) by Roy Vickers
The Yard (1923) by Horace Annesley Vachell
Tut Tut Mr Tutt (1923) by Arthur Train
Wheels Within Wheels (1923)
Whose Body? (1923) by Dorothy L Sayers
Why They Married (1923) by Mrs Belloc Lowndes