In an earlier post, I discussed the seventh edition of Rubicon Bezique, by Professor Hoffmann, circa 1908. Below are two scans related to the sixth edition of that booklet.
Using the same “dating” method that was applied in the post regarding the seventh edition, it is easy to establish a likely approximate date for the sixth edition portrayed in the present post. Even operating very superficially, it is obvious that the booklet appeared after Patience With the Joker, which was published in 1907. And we know that the book appeared before Bridge Varieties and Five Hundred, both of which were published in 1908 (and both of which were advertised in the seventh edition). So, the sixth edition appeared in 1907 or 1908, or very close thereto.
But wait! The sixth edition does not advertise Quinto, so it (probably) appeared before Quinto. Thus, the sixth edition appeared before the 1907 Quinto, and after the 1907 Patience With the Joker. So, it can be dated as 1907, sandwiched between two other 1907 booklets.
Having said, that, none of the above is certain. Maybe Patience With the Joker was really published in 1906. Maybe Quinto was published in 1908. Maybe Quinto was not listed for some reason other than not having yet been published. Those are just a few examples of things that might upset the cart. But I can easily say “circa 1907” as a reasonable estimated date for the sixth edition of Rubicon Bezique.
The sixth edition also carries other advertisements that might allow the date to be established more certainly.