And your measurement is derived from the known size of certain donor parts, correct?
That seems close enough to me. For all we know, the English model makers rounded certain measurements to the nearest convenient metric size... Or they made an honest mistake when building the nose, and got it slightly off.
Unless this puppy turns up at an auction somewhere (fingers crossed), I don't think anybody can call you out on it.
In your research, did you determine if anyone else has built this at studio scale?
-MJ