Wow that one is KOOL! It is for sure after WWII. Other than that who knows. It is very generic. A generic manual may help some:
http://www.dontai.com/wp/images/imperial-535-manual.pdf
You will want to clean it and oil it. Plenty of info on QB for you there. Here is a link for other Japanese zig zag machines from that era:
http://www.quiltingboard.com/vintage...s-t207877.html - this might be of help