I understand what you want to say and I can partially agree. But only partially. The manufacturer's specification of 500 kmh +/-25kmh does definitely not mean that the 109 reached 500 kmh but probably something less. I however doubt that all 109s will have been on the lower band. This would be basically impossible in terms of production. I also doubt that the manufacturer aimed at achieving 475 kmh, as was suggested earlier by somebody. This would be a dangerous policy for a private company because aiming at 475 kmh (meaning average performance of 475 kmh) would have meant that many many fully assembled planes including engine would have been rejected. Assuming a natural Gaussian distribution of performance this would have equated to a almost 50% rejection. Not one company can afford this. So my guess is that the average in tems of performance will have been well above the 475 kmh. However difficult to tell where it was. Probably somewhere between 475 and 500 kmh and the French test seems to concord with this. Perhaps they did have an optimistic plane. So one might guess that the average would have been at 485 kmh with a dispersion of perhaps 1 sigma = 3 kmh that is with a variation of +/-10 kmh at three sigma. This would make sense from a production point of view to have the lowest performing aircraft of a batch to be at 'average minus 3 sigma'.