Interesting, thanks Nick. A normal distribution curve suggests that a large deflection is not an unusual event which happens suddenly, rather a reading at either extreme as part of the normal spread. For the mean to be 8 degrees off to one side, this position can reasonably be assumed as the intended one for a 'perfect' strike working on the basis that most of the time, things would be done correctly. With a spread of 19 on one side and 14 the other, that isn't wildly skewed, and the sample size of 65 is large enough to be considered statistically significant. If there had been a clear lump in the distribtion at one extremity (which I was hoping for) then you could say this was a significant event, but a normal distribution rules that out. I don't think we can infer anything from this survey other than some engravers needed an eye test. Back to the drawing board.