I just checked Cooper and Pike's DETECTIVE FICTION: THE COLLECTOR'S GUIDE. According to this book's article on C. Daly King:
"Inscrutably, two definitions of the word "obelist" are given: "a person who has little or no value" in OBELISTS AT SEA, and "one who harbours suspicions" in OBELISTS EN ROUTE."
In addition to the three OBELISTS books mentioned, this book lists three other books by King featuring the same detective, "a young New York policeman named Michael Lord": CARELESS CORPSE, ARROGANT ALIBI, and BERMUDA BURIAL. I checked
www.bookfinder.com but all I found was a copy of the first for $850 and of the last for $1,750.