I recently acquired 3 schwinn collegiates 5 speed- one has straight top bar- other 2 have curved-looking for info on dating them and what styles were made- 1 of the curved models has a serial of gt100 ?- i am new to this craze, but had schwinns as a child- when did the bar get curved? and any one have specs onthese great bikes/

I believe the gt100 is actually the rear derailleur. The serial number should be stamped into the headtube of your schwinns, like this one:



I am assuming by "curved top bar" you mean the actual frame, I am not sure when that happened but I think you could by either one depending on your preference at the time.

Can you take pictures by any chance? Here is my 73 collegiate:

Once you figure out what your serial numbers are, here is the key to decode them:

https://www.bunchobikes.com/serialnumber5.htm

Could the RD be a GT200?



Pictures of your bikes will be very helpful. Welcome to C&V!

^ That's from disraeligears, isn't it? I love that site.

Yes. The best and most comprehensive of pictures of RDs anywhere.