I'm wondering if this is a described above or something else, i have had a look on here and most the links go to photobucket and are empty or no longer go anywhere, several online mostly sold by Fieldings, an image of one in Victorian decorative glass page 218 and some in this link but they all appear to be the same shape.
http://aarf.com/festeuben01.htm3 1/2 inches in height, 4 1/2 inches across the rim, there is a small polished pontil mark in the middle of the convex base approx 20mm in diameter.
Any thought's welcome, regards Chris.