Granny smith -- green, hard, break your teeth before they are ready, but when they're ripe they're pretty much the best of green apples. Excellent cooking apple. These aren't the variety Granny Smith, they are the offspring of Granny Smith.
1 year old bare root seedlings grown from Granny Smith apples purchased at the organic food store.
Photo Credit: Kolforn (Wikimedia), CC BY-SA 4.0 <https://creativecommons.org/licenses/by-sa/4.0>, via Wikimedia Commons