After looking at the pictures (if you click on them they will show up a little larger) I'm thinking that it is a machine made by National as seen at
http://needlebar.org/main/national/vs/vs06/index.html. I believe it to be what they call a Vindex Type 1. And as I mentioned before that Sterling was a badge that National (and others) used on their machines as seen at
http://needlebar.org/main/makers/usa...l/index.html#s. I don't see a shuttle to hold the bobbin, but maybe you just didn't send a picture of it.
The cabinet looks to be in great shape.
Your wife did a very nice job on her grannie's sewing box. It warms my heart when things like this are kept in the family.
Kind of interesting there is a "Pop Pedal Quiz" on another forum that seems to indicate that treadle pedal belongs with a Brunswick (another badge name used on National machines) or Damascus.
ETA: There is a manual for an Expert BT available at
http://www.doubleveil.net/zssmp/expertbt.htm should help some. That machine is an electric and the bobbin winder is in a different location, but I believe that the threading the upper thread would be the same for your machine.