It looks like 800-31(b)(7) was added after 1965.
The 1965 code says, in section 800-31 (b)(5):
[QUOTE]Electrode. The grounding conductor shall preferably be connected to a water pipe electrode. Where a water pipe is not readily available and the grounded conductor of the power service is connected to the water pipe at the building, the protector grounding conductor may be grounded to the power service conduit, service equipment enclosures, or grounding conductor of the power service.
In the absence of a water pipe, connection may be made to a continuous and extensive underground gas piping system, to an effectively grounded metallic structure, or to a ground rod or pipe driven into permanently damp earth. Steam or hot water pipes, or lightning rod conductors shall not be employed as electrodes for protectors. A driven rod or pipe used for grounding power circuits shall not be used for grounding communication circuits unless the driven rod or pipe is connected to the grounded conductor of a multigrounded neutral power system. The requirements for separate made electrodes for power and lighting system grounds, those for communication systems, and those for a lightning rod installation shall not prohibit the bonding together of all such made electrodes. See Section 250-86.
[ It is recommended that all separate electrodes be bonded together to limit potential differences between them ans between their associated wiring systems. ] [/QUOTE]
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