I have a Red Label FG-180 with serial number 1005423 inside but no other marks visible inside except a number "5".
I believe it was purchased in Boston in the summer of 1969. Can you tell me when if was manufactured?
Your guitar was probably made in late July 1969. You should find a large 6 on the other side with the date code near it. I'd expect 44.6.?? or 44.7.??.
Does the top of the headstock say YAMAHA or 3 tuning forks?