(and perhaps some people still refer to it )I believe the Swedish equivalent, a Calendar where nobility is listed was used to make sure that your children associated with and married the right kind of people!

Even I recall my parents frequently asking me. "What does his father do?" " Are they related to...?" That's what their world was like.
So I guess Sir Walter expected Elizabeth to marry from the selection in the Baronetage.And he knew other people were probably checking the Elliot family background.