Over 70% of the 429 White Circle titles were reprints of books first published by the parent company Wm. Collins in London. And the majority of these were in the mystery/crime genre, many first published in the successful Collins Crime Club series. Here are two authors from that series.
The first is among the most recognizable of the WC authors - Agatha Christie who had five White Circles. The second is Philip MacDonald with two White Circles. The only one of the seven with signed art is 228 by Margaret Paull. The artist for 365 also did the cover for Spillane's I, the Jury.
The Hollow (365) is the first Christie in 1948. First published in 1946.
The second is There is a Tide (426) in 1949 and reprinted in 1950. First published in 1948 as Taken at the Flood.
The third is Crooked House (478) in 1950. First published in 1949.
The fourth is A Murder is Announced (523) in 1951. First published in 1950.
The fifth and final is They Came to Baghdad (541X) in 1952. First published in 1951.
The first Philip MacDonald is Murder Gone Mad (207) in 1944. First published in 1931.