These are part of a set of Mustard-Glasses from France They were one of the few to actually do Sonic Glassware. The glasses originally contained mustard--which might contribute a bit to their hard-to-get status. No one uses mustard all that fast to warrant buying it a whole bunch of times in a row to collect the set. The rarest one is a Sonic & Amy one. How many others are there? The quality is reportedly quite good, with thick, tumbler-style glass used.