It all depends on which Martin scale length you're asking about. A modern Martin 25.4" scale length board would be 1.422". A Martin Shenandoah 25.4", or LMI 25.4" board would be 1.426". An older Martin 25.4" board might be 1.417", though these varied a bit in older Martins.
These are all nut to first fret measurements for a 25.4" scale board, without any compensation. They just each use different definitions of scale length - I'm working on an attempt to clarify these definitions, though not quite ready to publish yet. I'll keep you posted.
For the time being, A modern factory Martin 25.4" scale length is what most of us would call a 25.34" scale, which would have the 1.422" nut to first. Many fretboards sold as 25.4" are truly 25.4" according the the definition most use for scale length. These should have an uncompensated nut to first distance of 1.426".
As you can see, there's a serious lack of consistent terminology in this trade.

* Edit: - this was all assuming you were talking about their long scale. If it 's the short scale you're wondering about, that's a new set of numbers. Of course they would depend just as much on your perspective as well.