For me, the completely flat polished bottom would preclude it from being an early piece of Czech or Bohemian glass, as flat bottoms are not really a characteristic of their production. They typically have a dished pontil mark of some sort. I am hard pressed at the moment to think of an early example at all with a flat ground bottom from the early bohemian companies I am aware of.
It could possibly be later work, as later Czech work seems to be finished that way in some cases. Flat ground polished bottoms would also be equated with Italian glass finishing, although without handling it, it does not strike me as terribly Italian....
Wish I could be more help.
Craig