My mystery Libbey tumblers.

I bought a set of 4 of these cobalt blue tumblers from an "antique" store a few years ago and I was wondering if anyone knew the pattern name or how old they might be? They are made by Libbey, with the uppercase script L marking on the bottom. I've been trying to find more info on them and more of them to purchase but have had no luck. Any info would be most appreciated.