No earlier than 1975 on basis of derailleurs. Hard to tell, but front looks like a circa 1975-1977 Shimano 60 while the rear looks like a circa 1978-1979 Shimano 600. Crankset would appear to put it more towards the latter but the serial number will identify exact year.

While the hi-tensile tubing indicates an entry level model, the derailleurs and crankset suggest something more from the upper end of this range. The US models at this level and era were the Liberty and Americana. It doesn't quite match either and may be unique to the Japanese or Asian market.