In the antique and vintage sewing machine community if it does not have the Singer logo it is called a copy. A clone is a Chinese reproduction that has the Singer logo on it. Some of the Chinese machines were allotted by Singer and a lot of them are counterfeit. But if it looks like a Singer 15 with the dial on the faceplate and a different name on it then it is a copy, or better known as a Japanese 15. I have lots of company records from the Japanese based companies that made them and even in their records they are called "Model 15's". And I have probably the most information about the Japanese machines than anyone on the planet.
Billy