This is aclear blown glass round old fashioned in the Diamant pattern made by Cristal D`Arques-Durand France 1965-2008. The pattern has alternating length vertical marks all the way around the tumbler.
Up for your consideration is these royal blue or dark turquoise blue glass flat iced teas in the Driftwood pattern produced by Seneca Glass. Seneca produced the Driftwood pattern from 1953-1983 (when they closed).
This piece was made before 2000 in Ireland due to the Waterford mark has no seahorse. The Waterford mark is clear, legible, and complete as shown in the photos. The crystal is clear and healthy with no fogging or clouding from hard water or dishwasher exposure.