Welcome! Nice looking machine. It was probably made in Japan in the early to mid 50s. It's what is called a clone and is based on the Singer model 15. Yours has enough changes to it from the original design that I would say it was made about the same time they started going to zigzag machines. It should be a good quality machine. The best way to determine value is to take a look at your local Craig's List and make a determination from there. There are just too many variables to give you a good appraisal. The people asking several hundred dollars for similar machines are dreaming. Ignore those ads. Nobody gets rich off old sewing machines. There's too many out there.
Rodney