Do a search on the Singer 15 and you should be able to find a parts manual on Singer's Site if not I have one I can email to you if you need it. With it being a Japanese 15 it is hard to say what year it was made or who actually badged it for the company but the research is ongoing and one day we will be able to figure it all out. But until then if yo need anything just PM me and I will see what I can do.
Billy