One of the parts lists details the fitting of the cable grommet from VIN 1015593, from which it used to be assumed that the double cut fender became single cut at the same time. There do appear to be a number of genuine double cut fenders WITH cable grommet, hence as KP posted a while back, double cut fenders likely ran to late '69, with VIN numbers past 1015xxx, but probably not after 1020xxx.
Chris R