Please help me identify my tree's vairety

[gladgrad]

We bought an apple tree years ago at a nursery. I had never heard of the variety and have since lost the tag and don't remember the name.

They are average size and are green like Granny's but have a dark red splotch on about a third of the apple, they are juicy and tart and ripen in late July. They are a rounder apple with a thin shinny skin.

Any help identifying this variety would be greatly appreciated..

Thanks,

Gladgrad