I don't want go to out of topic too much, but according to this page http://www.departedflights.com/DCA95p4.html USAir operated Dash 7 into DCA in Summer 1995. What year did they retired them? I haven't seen and DHC-7s at DCA in 1996.
I believe the Piedmont DHC-7's stopped flying sometime after the summer of '95, however, USAir Express still operated them out of MIA when they acquired Paradise Island Airlines in 1996. That was rather short-lived though, because PD was flying under its own banner a year later before being absorbed into 3M.