In reference to James Shaw’s letter published in ATG No 2513 (‘To ping or not to ping, that is the question’,).
Glass is arguably the most esoteric category in antiques. Few examples bear identifying marks; original designs and permutations number in millions and copying/plagiarism has always been endemic in glassmaking.
So, most folks need all the help they can get when assessing the date manufacture and national origin of specific pieces.