I believe that what you have is the #1686 from 1937 - 1938
The catalog art for the 1937 and 1938 catalog uses a version of the engine from 1936. (Flyer is notorious for using artwork from previous years.) As you can see the engine pulled a freight consist and a passenger consist.
From your photo your set appears to be in beautiful condition.
Northwoods Flyer
Greg