... some so called "Sklo Union" pieces are very rare namely some colours.
For example Vizner's red vase Rudolfova huť - 13182/210 was manufactured in this colour only one day - number of pieces is in hundreds. Note also that in clear was inserted horizontal ribs in vertical waves, because of technological problems with smooth surface of waves.
Jindrich
www.webareal.cz/ceskoslovenskesklo