Leni - If I can squeeze in between the cookery posts, re your question "would it have been a one piece mould? I can't tell from the picture, but it's easy to check for yourself. Imagine the glass article as the jelly in a mould. If, on turning the mould upside down, the glass/jelly would fall out then the mould could be one piece and almost certainly would be because of the huge cost advantages.
Adam D.