I don't know if this has been posted before but here is some Catalog photos from turn of century. Shows how they are built and different models including a production quad bike.
Archive-catalog
http://www.cyclesmithy.com/schwinnarchives.html
Frank Schwinn notes
http://www.cyclesmithy.com/schwinnnotes.html
Collection of various bikes
http://www.cyclesmithy.com/rides_bikes.html
Archive-catalog
http://www.cyclesmithy.com/schwinnarchives.html
Frank Schwinn notes
http://www.cyclesmithy.com/schwinnnotes.html
Collection of various bikes
http://www.cyclesmithy.com/rides_bikes.html