To the best of my knowledge there were no Model 1907 slings manufactured between 1918 and 1942. Such huge quantities were ordered and delivered for WWI that they continued to be used right up until WWII.

I have an as unissued Model 1903 Springfield that was a NRA/DCM Sales rifle from June of 1936 that has a like new condition Model 1907 sling dated 1918.

I also have a B.T. & B. CO. sling that does not appear to have a date stamp or inspector initials.