it has Shimano 600 rear derailluer yes but what are the other parts? the crank, shifters, brakes? I can't tell from the pic but what is written on the little black sticker at the top of the seattube? it looks like a nice bike from here. a close up the dropouts and the BB might be more helpful to others to better identify it
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk