Congratulations. Fantastic that you have the manual, bobbins and accessories. My guess is that it probably is closer to a 1921 machine, but that is totally a guess.
It kind of looks like some of the decals may have silvered and consequently the finish coat is possibly compromised so be careful around the decals.
The decals on the bed look like
http://needlebar.org/cm/displayimage..._display_media
Another similar
http://needlebar.org/cm/displayimage..._display_media
Take lots of pictures if/when you take metal pieces off to polish. Do one area at a time. I have been known to not heed that advice and wished that I had. If that needle bar area is like the White machines of that era, I have heard rumors that it can be problematic getting it off and back together.
Lots of oil and plenty of patience are in order to bring it back to working order.
Other good resources for tips and hints can be found at
How to Clean Up and use a vintage sewing machine - videos by Muv and Fav
Cleaning and Reviving furniture(Sewing cabinets)
Enjoy the process. It really is a great feeling to get it all cleaned up and sewing again.
Janey - Neat people never make the exciting discoveries I do.