Did you get a manual and bobbins? I did some research and it looks like it is similar to a Morse 9500 and Necchi 543. It has an interesting bobbin case and evidently the bobbins for it are the ones that will fit Singer 306 & 319.
Threading for the Morse are at
http://www.sewusa.com/Threading_Diag...ng_diagram.htm It doesn't say exactly (or in a manner I can understand easily) which direction the thread goes, but I would guess that it goes over the top, from front to back.
Did you see
http://www.quiltingboard.com/vintage...g-t254070.html It looks like Margaret still had some problems. I'm wondering though if it might need to use a stack wound thread or a thread stand for the cross wound thread.
Janey - Neat people never make the exciting discoveries I do.