Euro Portugal 2009 Proof Set Error

Hi,
First post, and I'd be interested in your thoughts on the following.

I've recently bought a proof 2009 Portugal set on ebay, and checking them I noticed the following on the 10c coin.

First the negative, there's a blemish on the left hand side of the zero. (the mark on the 1 is dust on the coin case)

But secondly the reason for the post. One of the stars, top left, has not been frosted.

Is this unusual on a Euro proof coin, and if so would you consider it outweighs the blemish ? My instinct is to hang on, but I'd be interested in your views.