Austrian Silver Coins - What Causes Scratches Over The Bust

These scratches are NOT post mint damage; they are weight adjustment marks, or commonly known as simply 'adjustment marks'.
They are fairly common on European silver milled coins, and occasionally on English milled silver coins as well.

If a coin blank was underweight, it was re melted, but if it was overweight, some of the metal was filed off, and what you see here is the remains of those file marks after striking.

I presume most file marks (if weight adjustment filing was required), were completely obliterated during the striking of the coin. Not in this case.

I would prefer a nice coin without adjustment marks.
It is necessary, if describing a coin for auction, to mention them. I am sure that most intending bidders would see them as detracting from value, but are much less likely to lessen the value than equivalent post mint damage.

I'm not saying you're wrong but why would adjustment marks look like this ?

If I were the mint official and the coin was 0.5g overweight, why would I make a mark like a wire brush had been used several times ?

Wouldn't it be more efficient to use a standard tool to take a gouge out of the field ?