The cutoff date for original 2” numbers is around 1982, give or take:
§ 45.29(B)(1)
(i) An aircraft displaying marks at least 2 inches high before November 1, 1981 and an aircraft manufactured after November 2, 1981, but before January 1, 1983, may display those marks until the aircraft is repainted or the marks are repainted, restored, or changed;
