The Collaborative International Dictionary of English v.0.48:

Stem-winder \Stem"-wind`er\, n.
   1. A stem-winding watch. [Colloq.]
      [1913 Webster]

   2. Hence: (Fig.) Anything of superior quality, as was
      attributed to the stem-winding watch; -- esp. used to
      describe a stirring speech, as in the phrase "a
      stem-winder of a speech" or "delivered a stem-winder".
      [PJC]

WordNet (r) 3.0 (2006):

stem-winder
    n 1: a watch that is wound by turning a knob at the stem