Imprecise question; I can see there are two possible interpretations of dial size; the diameter of the dial alone when the dial is removed from the movement, or the visible portion of the dial that's visible once the dial is cased. I presume you mean the latter one; but it might be different in industry terms in the watch industry. Hope this helps you formulate the question precisely should you find someone who might be in the know.
Also, if I had a contact at VC, and s/he asked, "what's the genesis of this question?" How would I respond? If I respond, "a reader posed the question without stating its significance" that would put me in an awkward position.
Either way. Can't help you on this one. But our guess if around 28mm should be fairly close to the actual number. Good luck.