David, reading from Apples for the 21st Century, by (our own) Warren Manhart, 1995; LIBERTY: "Bloom time is from late early-bloom to mid-bloom. It has viable pollen..." You ask if it could pollinate a Gravenstein, from all I've read - not by itself. The Grav needs an extra chromosome that must be provided from yet another source of viable pollen. I believe past issues of our Pome News have described this in detail - beyond my comprehension, but that's been my take on it.
You may also look very carefully at that bloom time for Liberty, Gravenstein's are one of the earliest bloomers, and "Late early-bloom" sounds a bit iffy to me?
Here's the deal. Gravenstein is a Triploid variety. Meaning it has a third chromosome or a third somethingorother. In any case, this makes its pollen sterile and useless, even to other triploid varieties. Liberty is a diploid as are most apples. Liberty's pollen is suitable for the Gravenstein, provided that their blooming periods overlap. The Liberty, however, will NOT be pollinated by the Gravenstein's sterile pollen. Sounds like you know all this already. Unfortunately for you, Liberty is NOT self-fruitful and cannot pollinate itself. There are some self-fruitful varieties however. Yellow Delicious for one, but very scab-prone. Fuji, Gala and Goldent Delicious are also self-fruitful.
Ted Swensen sent me this list of self-fruitful varieties. Hope it helps 
Beverly Hills
Braeburn
Copurt Pendu Plat
Dolgo Crab
Dorsett Golden
Fuji
Gala
Golden Delicious
Jonathan
King of Thompkins
Liberty (most disease resistant variety known)
McIntosh
Newtown Pippin
Pettingill
Red Asdtrachan
Rome
Siberian Crab
Sierra Beauty
Transcendent Crab
Wealthy
White Pearmain
Whitney Crab
Winter Banana
Idyllwild
jafar
Marsha H
Viron
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