I had if fact already typed this just as jp's post went in.......but will now add my thoughts...............
"and this time I hope I get it right

. One of my books....."English Glass" by Sidney Crompton - Ward Lock 1967........has on plate 152, a variety of Bristol Wineglasses - "their colours ranging from peacock blue to dark green" and showing at the bottom left what appears to be a virtually identical looking glass. I'm the least knowedgeable person to talk on the subject of C19 wine glasses, so can only quote from the book. Unfortunately, sizes aren't given but looks to approximate reasonably well with the specimen shown here. I believe that this shape of bowl is called 'trumpet' - and would believe Dirk's dating to be not unreasonable, and although the plate in question doesn't actually give a date, that section of the book deals with early C19 material. Anyone else able to add to that?"