Thank you so much for all the info from Hajdamach! (I've only got the recent 20th Century book)
It definitely has deep cutting. I can't swear to copper-wheel engraving, because I don't know how to identify it specifically. I don't know about the extra polishing/worn out extra polishing.

I've got a wee wind-up LED torch.
I thought I'd try taking pictures beside some normal cut crystal glasses to provide a "quality control" for the image.
I think this has to take a little trip down south to see Basil. There are some water marks which need removed, and a couple of small chips (I think from the same dunt) also a tiny bruise on one shoulder. The stopper has miniscule fleabites around it's base, and sadly, a tiny bit has been knocked off the very tip of it.
And a serious polishing all over?
I don't think it's anything which cannot be fixed, and I think it's going to be worth restoring.
Birmingham is a good way towards Basil, I'm sure I have friends who would take it the last leg of it's journey.
That way, folk can see it and feel it. So much better than even the best images!
Ok, off to fight with the tent again.