See Yamaha FG Serial Numbers, Interior Markings, and Labels – 1966 to 1981 for more information.
Many made in Taiwan Yamaha guitars will have 2 serial numbers ink stamped in easily seen places, the brace under the fretboard and on the neck block. I’ve found most have ink stamped date codes on the inside, on one of the side panels. They are based on the Republic of China calendar starting January 1, 1912, the start of the Minguo era. This happens to be the same numbering system as Korea, because its fonder Kim Il-sung was born in 1912.
The first 2 digits of the codes in Taiwan made Yamaha FG guitars are the year based on the Minguo era. Year 1 is 1912, therefore the 61st year is 1972. Then the 2 digit Month. Then the 2 digit Day. Year.Month.Day 62.12.27 equals December 27th, 1973.
61 = 1972
62 = 1973
63 = 1974
64 = 1975
65 = 1976
66 = 1977
67 = 1978
68 = 1979
69 = 1980
1974 made in Taiwan FG-110.
Since the serial number on the brace is 40131535 (Jan 31, 1974) is later, the date on the side must be when that part was made.