In an early post I discussed Beaver Publications of Hamilton. At the time I had nothing more to add. Recently I came across a bit more information on the company - in the Library of Congress Catalog of Copyright Entries of all places.
Two separate entries note that Rendezvous in Vienna was published in 16 chapters Dec 4, 11, 18 1940, January 1, 8, 15, 22, 29, February 12, 19, 26, March 5, 12, 19, 26 and April 2, 1941. The only detail is "Beaver feature services, Hamilton, Ontario, Canada". Perhaps a weekly local newspaper? The book is dated May 1941.
I'm still looking for the four issues of Beaver's three books with illustrated covers. Rendezvous in Vienna has two and Cherchez la femme? and Modern Shorts have one each. They have to be among the most uncommon Canadian paperbacks.