Duchess Publishing & Printing Company was a Toronto based publisher of comics, magazines and paperbacks from the early 1940s until the mid 1950s. Here is one of its more famous books - Brigands of the Moon (c. 1946). No author is listed on the cover but the title page has John Campbell 1910-1971). This is wrong. The author is Ray Cummings (1887-1957) and the story was first published in the March to June 1931 issues of "Astounding Stories". Campbell was the editor of Astounding from 1937 to 1971 and this is no doubt how his name was attached to Cumming's book by an inattentive editor at Duchess.
The address on the back, 104 Sherbourne St, is in downtown Toronto. Sherbourne's original name was Duchess.