Having restored paperweights, I can confirm that bruises go quite a lot deeper than they look, especially in harder modern glasses. And many small bruises are not even visible until you start restoration. Google 'Herzian ring cracks' if you feel strong. and want to know what is happening in the glass. Lead glass is somewhat more tolerant, but there is always a risk of catastrophic failure with restoration. In terms of added value, I don't think it is worth restoring weights whose sale value is less than about £50, unless they are of sentimental value.