1968 Yamaha SA-50
Where JP semi hollow has begun
Legendary Yamaha SA-50, the frontier of Japan-made semi hollow made her debut in 1967, the same year that the highly sought-after SA-30 was released. Among Yamaha's semi hollow line-up, SA-50 followed the ancestry of SA-5 (1966) and SA-30 (Jun 1967), according to its release in Jul 1967. In their brochure Yamaha proudly advertised Yamaha SA series featured so-called 'adjustable neck', which must have referred to adjustable truss rod. Till then the truss rod had been made from wood, thus not adjustable. Replacing this with steel-based one was thought of as break-through technology. These first generations of Yamaha semi hollows continued with newer models such as SA-15 (May 1968) and SA-20 (Oct 1968), followed by half decade of gap before they gave up hockey stick-shaped headstock and introduced more modern, symmetric design (trying not copy Gibson's bookmark headstock, still following their incumbent concept.)
Please note this guitar dates most likely in 1968. Looking very fresh, she is graceful 47 years young. I can't help admiring the obsessive way of maintenance done by the previous owner. A Yamaha vintage collector would notice tuners, bridge and knobs are not genuine. Other minor issues include tremolo arm plastic cap missing, and buckle strap pin moved from the back to cutaway top. Notwithstanding, the ever rarer original hard case being shipped together must compensate all the glitches you found.