Singer didn't start manufacturing Featherweights until the 1930s. You can check the serial number here
http://www.ismacs.net/singer_sewing_...-database.html and see what model machine you have.
Most of the Singer feet for the older machines were interchangeable, so if you have a manual for one of the older machines, the instructions will probably work for this one or you can search the internet for a manual for that model machine.