With Shimano 600 parts, it's not bottom of the line, but those pictures aren't enough to really tell much beyond that. There's no logo other than schwinn anywhere on it on either side to give a model name? How about a serial number on the bottom of the bottom bracket shell (place the cranks -things the pedals are attached too- run through)?
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Bikes: 1996 Eddy Merckx Titanium EX, 1989/90 Colnago Super(issimo?) Piu(?), 1990 Concorde Aquila(hit by car while riding), others in build queue "when I get the time"