Hi,
You have a very nice Linn and Scruggs Rotary which was made by National SMCo. Not sure what parts you might need but here's a manual of the same model except motorized compliments of Smithsonian:
http://www.sil.si.edu/DigitalCollect.../NMAHTEX/0603/
Your Rotary uses 20x1 Rotary needles also known as Eldredge Rotary, Boye 21, DD or DD1221, and a few others. These needles are longer than the standard 15x1. Bobbins are special also having a large diameter inside hole. Hopefully you have the bobbin case and bobbins but they do turn up on occasion if missing. The Rotary models were top of the line and a search of National sewing machine co should turn up lots of background info.
Good Luck
Jon