TWE has been known to publish the unstrung SW of a good bulk of the more popular frames. As for whether those unstrung SW numbers are manufacturer-derived, or actually measured, I'm not sure.
As for measuring unstrung SW yourself from frames at your local shop(s), I would see if they would let you remove the carboard placard from one frame in each model racquet, just so you could know how much SW the placard and placard string adds, then substract it from each placard-included measurement, to get closer to the actually stock unstrung SW.