Given that I am not an expert on Skrdlovice/Beranek, my views are:
These are probably 1950s, and show signs, of being designed by the Beraneks themselves, or by one of the 10 members of the design team, mostly unknowns, with the exception of Jan Kotik, working under Veliskova, who was put in charge of the works, following the decision to keep the works, rather than liquidate it.
Now, before people get too worked up over value and collectability, the 1950's period, with the exception of items by Kotik, (such as his "propeller" vases), saw the production of items, strongly influenced by Murano, and the Scandinavian countries. This started to change late in the 1950s. Much of this work was produced in large quantities, and if Glassexport had a run on demand, these were frequently made elsewhere, for example Chribska.
Whilst it is true that during the 1960s and 70s, Skrdlovice gained a reputation for fine, innovative designs, from the newer generation of glass artists, it was also used as a place to trial designs, which would then be put into mass-production elsewhere.
Skrdlovice is known to have used several levels of production.
Unikat: Under Czech law, this term can be used for any edition of 10 or less items. These were mainly sold through the Art Centrum and Dilo gallery system in Czechoslovakia.
Small series: This, depending, on which sources you read, is generally seen as editions of under 500 pieces, or 250 pieces.
Large series: concensus is an edition of no greater than 1250 pieces.
However, and this is the major caveat, many items have been in production for MANY years. It would be unrealistic to assume that if an item went into production in 1968, for example, that in 2007, they will only now have reached 900 of 1250 pieces. The earlier the initial production date, the less likely it is to be important, if it still appears in the current Beranek catalogue, then it is not likely to become scarce, rare, or necessarily even valuable.
Even the fact of a major named designer, ie Vizner, does not help, as many Vizner designed items have been in continuous production since the late 1960s and early 70s.
This is an area, full of potential pitfalls, for the glass investor. If you buy the item because you like it, all to the good. If you buy it as an investment.... make sure you know precisely what you are buying.
Text © M. Newhall 2007