have to say I've not previously been aware of seeing the comment that matching Nos. were added by owners as an aid memoir for the servants - must speak to the maid again on that point;-)
I could be very wrong, but was under the impression that such numbering was for the benefit of the factory workers to help with 'matching' a given bottle to a suitable well fitting stopper, before leaving the factory.
It could be of real interest, and a way of helping to settle this issue of dating for matching Nos., if people here were to post pix of their bottles with matching Nos., provided of course that assumed dates of manufacture of said bottles is incontrovertible.
The copyists were busy, apparently, in the last quarter of the C19, and then again between the wars in the C20. Such bottle are now of considerable age, and will show sufficient wear to make accurate dating difficult.