The conditions of the exception to 250.140 that are relevant to the third wire are:
2. The grounded conductor is not smaller than 10 AWG copper or 8 AWG aluminum.
3. The grounded conductor is insulated, or the grounded conductor is uninsulated and part of a Type SE service-entrance cable and the branch circuit originates at the service equipment.
The fact that the third conductor is reported as green indicates that it meets the first option of condition 3, which is sufficient for the exception.
It is likely that the wire available in 1965 was either the SE cable with red, black, and spiral-wrapped grounded conductor, or the NM that was red, black, and green, or NM that was black, white, and green, or NM that was black, white, and bare.
The green wire is obviously insulated and appears to comply with the provisions of the exception which says nothing about color.