Wanted: 53-56cm Mixte frame of decent pedigree

According to Sheldon

A style of lady's frame in which the "top tube" consists of a pair of small diameter tubes running more-or-less straight from the upper head lug, past the seat tube, and on to the rear fork ends. A mixte frame thus has 3 sets of rear stays, instead of the usual two. A variant on the mixte uses a single, full sized top tube running from the upper head tube to the seat tube, but retains the middle set of stays. A lady's type bike that lacks the middle pair of stays is not a mixte.

     Mixte frames are stronger than conventional lady's frames,  particularly in resisting the tendency of the seat tube to get pushed  backward in the middle when ridden by a heavy rider.      
  In French, "mixte" is pronounced "MEExt", but normal U.S. bicycle  industry pronunciation is "MIX-ty".