hi Scott - providing matching Nos. on decanters I believe is really a C20 practise, and even then they're applied it appears to quality items only, and yes, I did mean those found on the stub of stopper and neck of bottle. It's easy to forget that the GMB is populated by folk from across the globe, and unconsciously I tend to make comments relating to U.K. glass, forgetting that practises differ depending on where people are.
Matching Nos. may well not apply everywhere - haven't a clue where your piece was made - easy to assume it was made in the country where it was found, but that's just guessing.
An issue with bottles is that so often when I find a decent one, the stopper isn't original, which disappoints, but that's life.
You're probably not too far wrong with your suggested date.
The down side the Andy McConnell's book is that it gives scant cover to C20 bottles - someone on the Board did say last year I think, that Andy was producing a revised volume to partly rectify that - but I don't have further details on that at the moment.