Hi Nev, panel and oval patterns were made by early pressed glass manufacturers in England, America and in Europe, yours looks like a very good candidate for a Manchester maker Molineaux Webb, Percival Vickers or perhaps even early Sowerby? Have you done a density test as Neil maybe able to help with the results.
I have some mol web piano feet which are Vaseline but have a streak of green that can be seen in certain light.
Cheers Mike