Ketubot 25: Are You Sure the Kohen Is a Kohen?

A focus on terumah, with the distinction of how that was applied in the land of Israel, as compared to in Babylonia - where terumah derabbanan was in play. Also, it was contingent on the "chazakah" status as kohanim. Note also different kohen practices as establishing kohanim as such, in the various places. Also, how were the kohanim actually established in practice? Various narratives illustrate the ways.