[Ned Milburn]

Very well described, Larry, and thanks for the concrete example of Martin's guitars.

Another factor to consider with string spacing overall, which is usually considered at the nut rather than at the bridge, is the string spacing in relationship to the diameter of the strings. Specifically, if strings are spaced equally centre to centre, the low E string will be closer to the fingerboard edge due to its greater diameter than compared to the lower diameter high E string. Hence, some craftsmen/women will set up instruments with string spacing with equal distance BETWEEN strings, and others equal distance from string centre to centre. Either option can be spaced with the outer edge of each E string equidistant from the fingerboard edge, or with their centers equidistant from the fingerboard edge.

None is right, none is wrong. Players that notice the difference (either of their own discovery or of having been pointed this out by a craftsman or other player) may find they have a preference. If you do notice you have a preference, then your preference should be stated when getting someone to work on your instrument.

Good topic, all in all.