It was the classic Schwinn straight bar Klunker that caught my eye and got me reinterested in bicycles as I neared retirement age. In my search for a Straightbar I found out that there was more than one style. I'll share what I think I know and hope for some input/insight from some of the sages out there. I believe there are four styles of Schwinn Straightbar frame. All have the double top bar in an over/under shotgun configuration. The upper top bar being arced and the lower top bar being straight ( why they are called Straightbars ). First - the early pre-war - all tubes are large diameter, the dropouts face rearward with chain tension adjusting bolts, the downtube is also straight. Tube joints at the headtube, bottom bracket, rear dropouts and seat tube are all external and done by hand (sloppy). The seat stays come together and attach to the back of the seat tube. Second - the late pre-war - same as before, the only change being the down tube which is now curved. Third - the early post-war - the fabled and much sought after "Fatbar". This is a transitional frame created by the changeover from hand built to electroforged made frames (the process for which Schwinn is famous, among others). All tubes are large diameter, the dropouts now face forward and do not have tensioning bolts. Tube joints at the headtube, bottom bracket and rear dropouts are smooth with no weld evident (electroforged). The seat stays now attach to the sides of the seat tube and the upper seat tube joint and the lower top bar joints are the only hand welded/brazed joints on the frame. Fourth - the late post-war - finally, the most common (probably due to high production ability). Same as the early post-war with one important change ... the lower top bar is now a smaller diameter tube with no welded/brazed joints at either end. The only manually blazed joint is now at the junction of the upper seat tube and the seat stays. I'm guessing that some type of electric weld was used on the lower top bar. Give me your thoughts.