It's a 15, just not sure if it's a 15-91 or another model of 15. The tension is on the side of the faceplate. The 15-91 will have a "potted" motor on the back (a black cover attached to the machine). It won't have a separate motor/belt. The 15-91s are nice machines, gear driven, vertical bobbin, takes regular 15x1 needles, short shank for the feet. I use mine the most out of all my machines. I paid about $25 for mine at an auction almost 10 years ago, and it was in almost pristine condition.