When it comes to Schwinns, straight bar or cantilever how can you tell what it is unless it's all original with patina ? Serial #s will give you year but will it also give model ? When you buy a frame (straight bar) w/out a tank how do you know what tank you need ? Seems a frame can be built up and be called whatever youde like to call it. DX straight bar, Hornet straight bar with added forks, fenders and chain guard could become one in the same..no ? And with cantilever frames being the same throughout the years could make things even more confusing. Are there differences in the frames throughout the years besides kickstands ? Thank you..stay healthy