Having looked up frit weights a bit I have realised they are tricky to id,would the broken pontil and clear glass narrow it down a bit?i'm not sure how the Belgians ,American ,finished off their bases,but would guess the Scottish would have a polished or broken pontil,the only other help I can give is the snapped off pontil is small neat and slightly raised,there is a lot of wear to the outer ring of the foot and the glass is bright and heavy in the hand .