Here's a post about a 115
Singer Model 115 Tiffany/gingerbread decals
maybe that will help determine the model. There are lots of posts and pictures of model 15s. I posted something here
Singer 66
about hand crank parts, and I have attached a picture of my 15 hand crank, which started as a 15-90. I have a recently acquired treadle table in the garage and was going to put this 15 into it and give it a spin. I do mostly repairs and have used this 15 hand crank a number of times since finishing it a month or so ago.