The sad thing of course is that wear is really a statistical game and can't be
applied to any one specific coin.
Studies like the Garonne one and others related to specific
hoards can provide
average circulation wear rates - such-and-such percentage
weight loss
per year - but these are averages for a bunch of coins. Any one coin can suffer far less or far more wear than the
average rate.
A nearly unworn coin was
likely buried or isolated shortly after it was struck, but it could also simply have circulated at a lower velocity in a less monetized region.
On a related note I have been looking for a reasonably priced copy of the Garonne book for years to no avail. it is the perfect candidate for a scan if someone could get permission.
SC