How did I miss this thread? Thank you for starting it Miriam, because I think I now know what the deal is with this sewing machine!!!
After looking over this thread I believe the first two pictures might be of a dusty 15 clone (the rotten little machine that started this whole old sewing machine obsession!!!) that fell into my hands several years ago and I couldn't find a lick of information on. I don't know what happened to the tension dial...I'm not sure it was ever there. I love the faceplate on this machine though, isn't it gorgeous?
The last picture is of an actual Singer 15 treadle from 1906 that the Husband purchased for me. Aren't I lucky?