Attributed Gilbert Stuart, 1756-1828. Portrait of a seated lady.

This portrait, attributed to Gilbert Stuart, was sold at auction (William Bunch Auctions) this month.  The estimated price was $4000.00 to $6000.00.  It only sold for $1300.00.  Can a genuine Stuart sell for such a minimal price?  Is it genuine?  The description for the portrait also includes: "Signed in pencil along with pencil sketch on back." Highly unusual, and suspect.
The provenance, "from the estate of former PA William W. Scranton." is also sketchy. My opinion on the authenticity of the portrait all things considered?
It has the style of a Stuart and is a beautiful portrait, but does not have the exquisite Stuart flair. Stuart exclaimed that his signature was the entire portrait itself.... hmmmm.  I do not think it is genuine.
But I could be wrong!