From the History and Genealogy of the Bieber, Beaver, Biever, Beeber Family, by the Reverend Irvin M. Beaver (Reading, Pennsylvania; 1939), page 515:

Mary Kneisley was the daughter of Hans Kneisley, son of Jacob Kneisley (Nissly), who pioneered into Lancaster Co., Pa., about 1729. Hans Kneisley's will, of Cocalico twp., Lancaster Co., Pa., probated 1757 at Lancaster, Pa., names Mary, wife of Conrad Beaver, of Virginia.

Conrad Beaver owned 410 acres of land on Pass Run in Page Co., Va., about 3 miles north of Luray Va., and died there and may be bur. on his plantation. Conrad Beaver was evidently a cousin of the Immigrant Valentine Bieber. Valentine came to America in 1768.

Mary Kneisley's Mauck family connection is from the Mock Family Research Center, and specifically a “Working Chart” for Rudolph Mauk.