GSC, your Cat 955 is a 955E, and yes, it was built in 1959.
The 12A series started production as the 955C in 1955 with 12A0001, then at 12A05793 in 1958, the tractor model became the 955E.
Production ceased in 1960 at 12A08418, when the model was replaced by the 955H with the S/No prefix of 60A.