Most of the time, it's a 733 from what I've observed.
He's asking where it's coming to BWI from, not what type a/c it is
1663 looks like another of WN's 5-legged runs: BWI-AUS-ELP-LAX-SJC-PDX. Can't tell where it's coming from though.....perhaps one of the WN guys can look it up. You might be able to get some idea by checking Flightaware later on: since 1663 is scheduled out of BWI at 1400, check for flights that arrive around 1330 (and make sure that the incoming flight doesn't correspond to an outgoing flight with the same flight number).
Tom at MSY
"The criminal ineptitude makes you furious"-Bruce Springsteen, after seeing firsthand the damage from Hurricane Katrina