Thanks for the info. No the machine was not an industrial. The one my wife was trying to remember is the one she learned to sew on so long ago.
She distinctly remembers it was the old black style Singer, with a knee bar control and the round plate around the SL / R lever, and she thinks the tension was on the front, not the face plate. And she doesn't think it had a belt. But she can't remember for sure.
Knowing her mom and the way she only bought the best of things my guess is a 201-2. But there is no way to tell now.
Joe