Preheat oven to 350 degrees F (175 degrees C).
Cream together sugars, shortening and butter.Mix in the eggs and mix well.
Stir in flour, cream of tartar and baking soda.Stir in vanilla and salt and stir until well blended.
Roll dough into walnut sized balls.Flatten with glass bottom dipped in sugar.Bake for 10 minutes.
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