Welcome to Quilting Board. It looks like fairly straight forward threading for those of us familiar with vintage machines. I don't know, but perhaps one of these threading diagrams may be helpful.
https://web.archive.org/web/20160404...ng_diagram.htm
https://web.archive.org/web/20160403...ng_Diagram.htm
Oh, you probably know that it would have been made prior to 1957, since that is when the department store closed. I would think that probably even earlier since it is straight and zigzag only machines. Neat that you have a needle position lever (LMR) I can't tell for sure, but it probably takes high shank presser feet.
Janey - Neat people never make the exciting discoveries I do.
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