thanks Martyn - my personal thoughts on your dealer's comment are ....................
For British lead based cut glass material there should be a noticeable sharpness on almost all examples up until the first or second decade of the C20, when it became the norm to use acid to speed up the process of removing the grinding marks from within the mitres etc. This use of acid on cut glass, was a C20 innovation and completely separate from the C19 practice of using an acid mix of hydrofluoric/sulphuric, as practiced by the cameo workers and intaglio engravers.
As for the colour or hue of the glass, I've noticed there are people who will swear blind that some early C19 glass is found with a clear white appearance, but as I've thought often, I'd rather have a nod toward a leaden hue rather than something that's too bright/white. But here my comments are rather subjective, and I can't substantiate, with provenance, my thoughts one way or the other - but I sense there might be more pieces out there, originating in the early C19, that have a grey tone rather than white/bright.
Irregularity of cutting is a very good point, and I'd go with this suggestion as being on of the better pointers to age.
Unfortunately, in the 1920s there was a renaissance/passion for olde worlde styles, and if you read McConnell's entry for Mrs. Graydon-Stannus - for example - it's frightening to see the extent such copyists went to in order to produce C20 glass that looked more like C18 glass, than C18 glass actually did. Hers was perhaps an extreme example - the lady was a forger who set out to deceive, deliberately - but there have been other C20 makers such as W/Fs., E & L., and Walsh, who made 'Georgian style' glass, in the C20, on an industrial scale - much of it tinted or coloured to make the copy more akin to the originals.
Hill-Ouston's reproductions in the 1930s replicated the Bristol Blue and amethyst colours on Georgian patterns on a massive scale, much of which was apparently sold in the States - so, you can imagine the problems that material is now causing.
To quote McConnell again …...…...…..""Most British fine glassworks made extensive ranges of 'Georgian' reproduction wares between 1900 and 1939.""
With respect to your dealer in Worcester, I'd still maintain that differentiating between originals and copies of the material we've been discussing is more difficult that is imagined.