Originally Posted by T-Mar
Yes, that's 1st generation 600. The three arm, touring oriented cranks didn't last long. Take a close look at the rear derailleur and you'll notice how inespensive it is relative the 600EX of only two years later. The only casting is the back/upper pivot housing. The parallelogram and foward pivot housing are formed sheet.
Sorry, I don't have any Apollo catalogs. Though I sold Apollo, we only carried the entry level models. The higher end Apollo (and Sekine) didn't quite cut it compared to the competition, though the entry level models were great. Given the era, this model was probably 2nd or maybe 3rd from the top of the line. With full 600 and a butted, CrMo frame, I can't imagine a steel rim being original.
T-mar are you sure that rear derailleur is first generation? I have a couple 600s from 1977/1978 (date coded bh and ce) that don't have the arabesque-ing that I though came later.