A quick check to tell if the Mdl 15 you are looking at is a later Chinese or oriental clone is the finish. These later clones are really shiny with garish, gaudy, really fancy decals. Way more over the top than any of the originals or Japanese clones.
Here's a link to Singer India: {
http://www.singerindia.net/Straight_Stich.aspx?id=1 } with some pictures.
Joe