Hi! That's a real pretty one that you've just gotten! It looks like one of the model 15 versions, but not sure which one.
The knob on your other machine (that you mentioned)....is that a knob that controls the length of the stitches? Is it possible that your machine doesn't have a reverse function. I have a singer 66 that has a knob like that (in a different place) and it only controls the length of the stitches and I can't do reverse at all.
ETA: Muv has a wonderful Youtube video that shows how to thread and load the bobbin on a model 15. Here is the link:
http://www.youtube.com/watch?v=H2tii...eature=channel