Now that you’ve drawn attention to it, the ones without a handle make more sense to me as a potential linen smoother. You could apply pressure by pressing down with your weight through the palm, so would it need to be really heavy? The handle position isn’t very ergonomically positioned for heavy work either, can you imagine how awkward it would be using a modern iron with a vertical handle? Also it doesn’t seem practical to have a convex bottom on a large heavy smoother, if that’s what it was, it would be difficult to control if it wobbled around. I can see a small one with handle might be useful for collars or other details.
Yes I have been thinking about actually using these that way as well, and the pressure as you say and I concur. I just cannot see it.
Also, I've been searching and searching and from what I read (online, not a researcher, just trying to find information and get a feeling for the times) I can't imagine the masses ironing their linen. So if anything was used to smooth small articles like collars etc then I suspect they would have been used in big houses for the rich.
I am beginning to wonder if they were used for leather working of some sort. Maybe to do with riding or perhaps shoes? I don't know - just thinking outloud.
The only mention of early 1700s I could find for use of a glass mortar and pestle (did not say how big the pestle was or what shape) was the mixing of ingredients trying to make Quicksilver ( a dangerous thing to be doing at the time as I know from reading about silvering mirrors). And I think that Alchemist/Chemist was in Amsterdam from what I read (original text 1745 I think).
I don't think he'd have been using a glass pestle anywhere near as big as 10cm across and weighing around a kg I'm guessing for mine. Might be less but it's heavy:
https://www.google.co.uk/books/edition/The_Philosophical_Transactions_and_Colle/er2zqe1GgAAC?hl=en&gbpv=1&dq=glass+pestle+1700&pg=PA720&printsec=frontcoverAlso mine and some others are black glass. The Woodchester Glass House seemed to be making transparent glass so I wonder where the glass for the black glass handled 'linen-smoother' came from?
What made me think about that is there is a some information about the fact that the medieval ones came from Melle in France. I didn't totally understand the research but I think they might have been made with slag from ore processing or something.
They have been chemically analysed.
That made me think hence looking up the black onion shaped bottles. But again I couldn't find any that really reminded me of my handled object. Even the lucky find of the one in Bonhams looks green.