sounds like a Super Sport.Schwinn built a lower grade cro-mo tubed line along with the Paramount.They did so from the beginning.Sometimes you see very old New Worlds with the three piece cranks.Also the original Town &Countrys(tandems) were Cro-Mo tubed.Last to be added to this line of bikes was the Cro-mo BMX line.
Yours would be a great bike(if a SS)It's easy to add a 3piece crank using a BMX BB adapter.