Я не спец в серийниках той поры, но судя по инфе Гибсон made in USA фигурирует лишь в 1970, а по цифрам выходит 71-72 год. Нет?
In 1970, the words "MADE IN USA" was impressed into the back of instrument headstocks (though a few instruments from the 1950s also had MADE IN USA impressed into their headstocks as well). Year (s) Approximate Series Manufacture
1970, 1971, and 1972 100000s, 600000s, 700000s, 900000s