thanks Kevin. Perhaps yours was owned by a member of the Temperance Society
I have some table glass from the late C18/early C19, and several spirit squares, and as you say there is usually a greyish/steel tint - but I'm not sure that I'd be able to say where a grey tint ends and a blue might take over - should I ever see something with a blue tint that is.
I'm not well up on this 'blue myth', but makes you wonder whether someone got carried away looking at a strong grey tint, perhaps in the wrong light, and thought they were looking at blue.
Once you've seen Georgian lead coloured glass, it's unmistakable, and as you say, it has nothing like the brightness of modern glass. As to the acclaimed better sparkle of C18 cut glass, it may be true - possible because of the lack of acid polishing which seems to have become an habit of economy in the C20 when cleaning up the cutting, and dulls the sharper reflective qualities.
We mustn't forget that most of the big C20 factories produced copies of ealier patterns/designs, prior to 1940 ish - W/Fs, Richardsons, E. & L. and Walsh amongst them - and it was the Georgian fashion they seemed mostly to copy, so your example might well be from such a source, and let's not forget that these names did produce high quality glass, whether contemporary or historic in style. Unfortunately, I've never knowlingly seen such 'reproduction' piece from any of those factories, but had assumed that the colour would be brighter than an original.
However, not so apparently, as Andy McConnell cites a page from one of Richardsons catalogues dated 1916 on which it clearly states that "reproduction of a George III decanter etc. etc...........is to be made in old glass, and with stoppers rough fitted". The 'old glass' implying that they where replicating the C18 colour - and you may also be aware of Andy's story concerning one Stourbridge maker who employed someone to rub the feet of wine glasses on a doorstop to deliberately age the pieces.
One apparently reliable method of determining age on decanters is to try sliding a piece of paper under the base - where the decanter doesn't touch the table the paper should slip under, and therefore the base (of the decanter) should appear (in that area) devoid of wear. I've never tried it - my few pieces seem covered in dull matt wear all over their bottoms.
I agree that colour and wear are probably the most critical characteristics that I'd look for when assessing age, but less than perfect cutting is also important, along with seeds and lack of symmetry in areas like the neck, but it seems from Andy's comments that colour may be less reliable than we'd thought.
Having read Andy McConnell's posts above, you might be forgiven for thinking that his 'Decanter' book would have provided some illuminating new information on Mrs. G-S 'nefarious' activities on the alleged reproduction of Irish glass (not the 'Gray-Stan' material) - however, not so, and in a book running to something like 575 pages he offers no more than nine and a half lines of previously published information. He also reproduces the same picture of the lady as Hajdamach's plate 171. Can only assume that additional unpublished information proved impossible to come by - but who knows - I understand Andy has declared his intention to reprint the book with a view to providing more information on C20 material - fingers crossed.
Regret I can't really comment on your decanter - I don't have any Irish examples - old or reproduction.......but, having just looked through Phelps Warren I can appreciate your difficulties. All the features on your decanter seem to agree with the originals, but then I don't have your one in my hand, and this might make all the difference - seeing it in the flesh so to speak, so suggest you contact Andy
P.S. Andy McConnell's book is invaluable - I wouldn't be without it, and my comments about the G-S matter were simply one of surprise bearing in mind Andy's earlier discussions requesting information on the lady and linking this to his book. I know it's expensive - let's hope the reprint isn't too far away.
Refs. 'The Decanter' - Andy McConnell - 2004
'20th Century British Glass' - Charles R. Hajdamach - 2009
'Irish Glass' - Phelps Warren - 1970