Some additional information regarding m's link showing the George III half pint decanter .........
Barrington Haynes book - to which reference is made for provenance and for dating pieces which are accompanied by a 'press-molded stopper somewhat pagoda-like' - was written originally some sixty odd years ago. Haynes wrote that these decanters seem to have been made in Scotland or (possibly) Tyneside, and were decorated variously with crude engraving, bright foral bands of paintwork, gilding and flashing, and he does give the pagoda description to some of the press-moulded stoppers.
Andy McConnell's 'Decanter Book'- published less than ten years ago, also discusses these particular bottles - which in the trade appear to have been called 'Newcastle decanters'. Painted, flashed and crudely engraved bottles are shown in McConnell (including pieces with oak leaves), and the examples include either pressed 'pagoda' or mushroom stoppers only.
McConnell also quotes the Barrington Haynes illustration (whose pictures were all b. and w.) although the bottle in question was a plychromed enamel version.
However, the point about all this is that opinions regarding origin appear to have changed in the last half century and according to McConnell these things were made "across Europe, probably excepting Britain" - the vernacular name deriving possibly because they were imported through the port of Newcastle-upon-Tyne.
McConnell quotes origins as possibly Bohemia (flashed bottles) and Spain for plychrome examples. Denmark is also given as a source.
Dates are quoted as c. 1830 - 1840, rather than the slightly earlier period mentioned by Haynes.