This is a beautiful, pre-designer Blenko base in Emerald Green. The first designer for blenko was Winslow Anderson in 1947. Emerald green was produced from 1935 - 1953, so I believe this piece was made before 1947. The vase stands a little over 8 inches tall.
It has a few air bubbles in the glass. There are a few flaws from production in the glass (see photos). It was dirty on the inside and I cleaned it the best I could, so there may still be some residue or water marks on rhe inside