Good call on the needle position.
A lot of times when there are two knobs or levers next to the zigzag control, they are usually to lock the zigzag control.
It looks to me like threading a Singer 15, with the exception that the needle would be threaded from front to back.
I'm not positive about the extra holes in the upper thread guide.
Usually there is a thread guide on the front arm or nose of the machine to guide thread to the bobbin tension guide under the bobbin winder.
Janey - Neat people never make the exciting discoveries I do.