I have not seen any retail literature for the 1940+ models at all.
They seemed to be surplus issue with no rhyme or reason as to whether they were equipped with a Arrow type tank or the Speedline type tank.
The down tube configuration was also mixed, being either curved or straight with either tank fitted. They all seemed to be painted the same, Off/Bone White and Brick Red. They almost always were badged, Shelby Supreme.
The 1938/39 models adhered to a more strict convention. Straight downtube meant Shelby issue and curved downtube meant Gambles Hiawatha issue.
The individual tank styles of both didnt cross over between the two frame styles.
I'm not sure if the Bone White was used on the earlier models. It can look similar in pictures to the Straw color, but was actually quite different. The Straw color had more of a Butter Yellow hue.
PS. For some reason, the surplus bikes were not equipped with a horn. The lack of a horn button is also an indicator that your tank came from a 1940 model.