it can do if you watch the gaffer making it
I didn't quite mean down the exact month or year, but a given decade would be good enough.
obviously I'm buying bottles from the wrong place
- it could be my memory, and it may be the case that I have seen numbers on that surface and forgotten, but certainly for me it's unusual - most commonly they are on the stub or neck of the stopper. If you think about it, marking on the mating surface, you'd imagine, wouldn't be the first choice of location in view of potential wear that might over the years obscure it, but obviously they did and the one shown here remains legible still, though as for age I'm not sure.
I'd suggest that if either the stopper or the bottle lack a matching No. then they didn't start out life together - alternatively, the original stopper was lost and a replacement made, professionally. At least for the C20, a correct stopper should fit with a smooth non-wobbly fit, then lock,
but according to the books Georgian/Regency stoppers were less of a good fit - Andy McConnell's book does help with some of this information.
I'm sure that if paper work on this subject did exist someone would have told us by now.
Many moons back I had a heated argument (so nothing new there then) in north Wales with a guy, in an antiques shop over just this subject of matching stoppers. He was buying an 'old' decanter, and I commented that he should make sure both parts had matching Nos.
His reply was that the workers would simply spin one on the treadle lathe to make it fit the bottle and that was good enough - they didn't mark them. I don't remember the age of the bottle he was buying.
Rarely I have seen Nos. that had an old appearance - a 'type face' if you like - typography and style of a late Victorian/Edwardian font.
Anyway, now waiting for the hordes of pix from members showing matching Nos. on Georgian and Regency decanters and their stoppers.