For some reason major errors on mercury's, buffalo's, and standing liberty's tend to be much scarcer than other series. Why this is true I do not know.
That is sort of odd, isn't it. I've got well over 3,000 Mercury Dimes and the main thing I've found in the way of errors is that about 25% have rotated reverses. Anywhere from a few degrees to about 90. None are off centered at all. Seldom any RPM's, double died or some of the more common type of errors. Lots of large and small mint marks are popping up lately though. Sort of the same thing with Buffalo Nickels too.