Martyn - apart from the fact that decanters have a limited following here, think also there's a limit to what is discernible - in terms of 'hallmarks' etc. - that can be seen on the screen, particularly when phone pix aren't perhaps the best.
As we've said, the face value appearance of a bottle is useful, but there are other features that are essential for determining if something is genuine period, and even then people will argue amongst themselves.
Perhaps time to view some antiques fairs and make comparisons - or museums etc. On this one the 'wobble' aspect sounds unusual - don't recall having a bottle than wobbled, and doubt that 'millions' (referring to genuine c. 1830 bottles) could be corroborated, though no doubt many designs were common.
Other features to consider are ................. colour, seeds/stones, discolouration inside the body, is the cutting sharp, can you see grinding marks within the mitres .................. but even then separating something made c. 1830 and 1890 can't be easy. Some people will suggest that the colour of the glass is most important feature from the Regency, then again others will say many bottles are known where the glass lacks any leaden hue. Most things that are genuinely old, have a certain something that can be seen, but perhaps not described easily.
Can't recall - do you have Andy McConnell's book?