I think there are a few of us in here that know the owner of this Grant quite well.
Its a stranger story than you might imagine as both the correct lack of paint and the holes are of historic importance and have a direct bearing on the capability of British tanks from Centurion up to the present Challenger 2.
You'll notice the holes don't overlap, except for mistakes (!); they were all intentionally and carefully designed being made post war by WWII German shaped charge weapons. . . . . . . . .
R.