After looking at the first photo of your tractor, it narrows down the year to either 1939 or 1940.
Notice the design/style of the right brake on your tractor.
Compare it to the photos below of the right brake on "Uncle Earl" our 39B.
The photo below shows the right brake on "Lazarus" our 40B.
Your tractor will also have a 4 speed High/Low with reverse.
Hope this helps.