Hello Katherine,
Isensee belongs to the parish of Osten located between Cuxhaven and Stade.
In 1745 for example following persons with surname Alf/Ahlf lived in Isensee:
Frerk Alf
Peter Alf
and in other villages of the parish of Osten:
Augustin Alf
Hinrich Alf son of Johann Alf
Barthold Alf
Johann Hinrich Alf
Johann Alf son of Claus Alf
Marx Alf son of Johann Alf
Johann Alf
Peter Alf son of Peter Alf
Hinrich Alf
Johann Alf son of Jürgen Alf
Albin von Spreckelsen