Anonymous source published in Sentinel of Freedom says Joseph identified hand writing of Abraham on papyri.
"A Convention of Mormons.—Mr. Van Buren," Sentinel of Freedom 43, no. 48 (June 2, 1840): [4]
I must say a few words now about the mummies. The Prophet has four, which were purchased by the church at an expense of some two thousand four hundred dollars. He also has the Papyrus, and often astonishes his followers with his great gifts by translating the writing. He says three of the mummies are Pharaoh, his wife and daughter. As he was in doubt about the fourth, a gentleman from the East, who called on him a few days since, suggested that it might be the mother of Moses, which the Prophet thought not improbable.
On one of the Papyri, he shows the hand writing of Abraham! Now all these things help to carry out his system, and his great show of learning or gifts has mighty effect upon the minds of his deluded followers.