Sue, can I just flag something up for clarity please... Sklo simply means Glass in Czech, so the fast answer is yes it's sklo (glass) - if (as I'm guessing) you're meaning is it Sklo Union (i.e. made by one of the Czech companies under the SU umbrella) then calling it simply Sklo isn't correct. Hope this helps.
Having said that, I can't see anything particular which would make me think this is Czech made (although others may know better). Out of interest, why would you suspect Czech?