The white transparent “Ghost Apple”—aka. “Apple of Saint Peter”—is a pale thin-skinned variety of the Russian Petrovka group that ripens around the beginning of the Feast of Saint Peter. The bone-colored fruit with its transparent flesh was offered to widows and orphans (“first fruits”); and it was placed at the graves of the winter’s recently deceased, as a symbol of the purity of God’s grace and mercy. The Ghost Apple has also been used in fortune telling; and has been associated with Baba Yaga, the witch of Russian folklore.
These Ghost Apples are from Coudersport, Pennsylvania, likely brought as seed with Russian immigrants.
– From the “heritage apple site” (tumblr)