You don’t say what your piece of glass is. Try the website of Capredoni Glass, they use the dragonfly as a mark. Alfred Capredoni made glass for Dartington. The son Chris runs the business now and in the early years they made vases etc. but most of it is paperweights and crystal animals now. also someone wrote that they found a dragonfly on another piece of glass but it was’nt Capredoni and the Glass encyclopedia does’nt know who it is.