A few pics on how to spot the FAKE Glencairn Glass. Please Read Edit at Bottom
One on Left is FAKE and One on Right is REAL
See how much Thicker the one on the left is. Its almost as thick as a pint glass. And has a heavy feel to it when picked up.
Fake one has the letter scratched in
Real one would have the letter etched in.
So when you when got it filled, it when look like this at the bottom
EDIT- Both Glasses are Real. One on Left(Fake) is a Just a Older Style of the Glass and One on Right(Real) is The Newer Style of the Glass but both a 100%REAL.Sorry