Schwinn experts, I need your help. I picked this up at a sale, just as you see it. I could use an upright so this one might be a keeper. But I can't figure out what year it is. The rear derailer is a Suntour GT with no date marks. I could not find date marks on the Sugino crank or "Schwinn Approved" brakes. The front badge says "Schwinn Approved Taiwan". The serial numbers are, right rear drop out "G0780" and on the left, 741798. There are no numbers on the bottom bracket housing, the head tube or the seat tube. I'm guessing it's a mid-70's bike, but I'd like to know for sure. Any help is appreciated.
I also want to share with you how I, Kaptain Klutz, thought I'd found a date code. I searched all over the rear derailer, finally, I found it, two letters "LO". But that seemed kinda strange because I know "O" is not a month code. Then I found another two letter code "HI". You guessed it, I found the labels for the DR stop screws, Duhhh!