Someone on another thread (will post a link if I can find it again) posted that Singer at times would make machines that were "blank" -- no Singer logo on them -- so companies could put their own logos on them.
This one looks like a "blank" Spartan that has been decorated and named Cinderella!
Edit: Ok, found the post. Scroll down to BARBM32. They were Singer knockoffs.
http://www.quiltingboard.com/t-118313-2.htm