Founded in 1935 today Michael Joseph is an imprint in the Penguin General division of Penguin Group UK.
All of the WC reprints were from the last four years, 1949-1952. Here we'll look at the first four. Collins usually described a book's genre. Trottie True is a "novel", the other three mysteries.
White Circle CD 377 - 1949 (originally published 1946)
White Circle CD 402 - 1949 (1947)
White Circle CD 467 - 1950 (1949)
White Circle 480 - 1950 (1949)