Fabulous one - I have several of these and I count them as my top pieces. They are what the Germans call "Badebecher". You needed one when you went for a "Kür" in a "Spa". You traveled to the grand hotel (the best ones were of course Karlsbad, Marienbad and Baden-Baden) but any town with "bad" will do. You then got yourself a measured goblet, and do the rounds "partaking the waters". The Kür is a sequence of perhaps 10 days in which you start on small quantities the first day, and drink buckets of the stuff towards the end. I have several with a double measure: one in ml. and the other in days.
The amethyst degrading to clear would probably be by Moser. I have a panel cut oval one, blue drgrading to clear with "Karlsbad"on it - every inch a Moser quality.