Shimano New 600EX (aka Arabesque) was 1978-1983. During the latter portion of the time range, the 600EX models were the Gran Tour and Aristocrat. Both were decent mid-range bicycles but as noted by WGB they did tend to scrimp a bit to get a cost advantage on the competition. They still spec'd 27" wheels, used slightly stouter tubing and didn't have as many braze-ons as you might expect. Oh yeah, some of the later ones also had the funky, proprietary, Ross safety dropouts on the forks.