Yamaha Nippon Gakki No. S-50 classical guitar - 10 bucks Junk store save!

I bought a Yamaha S-50 "Dynamic guitar" from a junk store in Japan for 1000yen (10 bucks) and cleaned it up. Hear it here! Vintage (old) Yamaha Nippon Gakki classical guitar. I try talk about my research into the S-50 and try to find out when it was made.