Duchess of Oldenburg
Duchess of Oldenburg (a.k.a. Duchesse d'Oldenburg, Duchess, Borowitsky) is an old Russian apple variety, which is originated in Tula region of Russia in the 18th centuary. Duchess of Oldenburg is very cold hardy and can be cultivated in hardiness zone 3. It ripens in August and can be used for cooking and fresh eating. Trees are 5-6 feet tall.
Flowering Group: 2, can cross-pollinate with flowering groups 1, 2, 3
Hardiness Zone: 3-8
Calculate to see if your zone falls in this range here