Looks like a quality bike, probably mid-level racer from the late 70s, early 80s based on component selection. Champion No. 2 tubing , forged dropouts, and Shimano 600 Arabesque drivetrain are very good things. That said, Sekine bikes are not particularly collectible. I would say $150-$200 USD wouldn't be too bad of a price, all things considered. Ditch the dork disc and you might eke out another $10.