Hi,
The colour is not an IoWSG colour, the glass itself looks far too thick, the rim looks wrong, even when it was simply gold leaf used it was more diffuse and all over the piece.
The "coach-bolt" pontil mark was achieved by putting the blob of glass on the bottom and quite literally using a coach-bolt head to round the inside of it. There just happened to be a big metal coach-bolt lying around.
I was thinking the way the leaf is applied it more along the lines of the foiling Iestyn Davies used at Stuart Strathearn after he left IoWSG in the Ebony and Gold range - but Stuart Strathearn have polished rims and the black is made fron a different shade of deep purple. (or is it red? sorry, a bit brain-fried).