Liliput has produced 2- and 3-axle coaches both with open and closed platforms. They're to release two new sets, although the lettering makes them era III (safe for the luggage van):
http://arwico.ch/123/detail/167328/SBB-Oldtimer-2---3-achsig-4-teilig-C2,-C3,-B2,-F3.aspx
Models with the old emblem can still be found in some places.
As stated above, Brawa offers rather nice 4-axle and 2-axle coaches, but they would have been rather thin on the ground after WWI. If you suddenly found that you're a dentist or belong to the leisure class in general, there are numerous models in brass to suit that era...