Apartment Therapy suggests that they are vintage glassware; the Umbra site says "hand selected". Designers doing such a thing in small quantities is not unheard of, but for a company the size of Umbra to do it is amazing; big companies worry about consistency, packaging, all kinds of things that would make doing something like this more trouble that it is worth to them. Impressive.
Mismatched Glassware Unified by Sandblasting
Take mismatched glassware. Sandblast it. Now they are all united with a similar frosted exterior. The Frosine glasses were designed by Michelle Ivankovic, senior designer for Umbra. Apartment Therapy suggests that they are vintage glassware; the Umbra