Thanks for the comments.
David, I described the colour as 'off-white', but I should have been a little less ambiguous. Sorry. I meant that it is grey. Quite a bit greyer, in fact, than my sole piece of genuinely old glass - a carafe from the first half of the 1800s.
Ivo, the stem is a little seedy - just not as much as the bowl. The foot is the same, containing only a few bubbles. That said, the bowl does have some large areas, probably just under half of the surface area, that are lacking significant amounts of bubbles too.
Hopefully the last image shows the stem a little more clearly - and I've also tried to make the colour as 'true' as possible (although my photo set-up is backlit, which tends to knock out subtler shades of grey in clear glass).