sheepskin

definition: a document certifying the successful completion of a course of study
example:
speech part: noun
synonyms: diploma
definition: skin of a sheep or goat prepared for writing on
example:
speech part: noun
synonyms: parchment lambskin
definition: tanned skin of a sheep with the fleece left on
example:
speech part: noun
synonyms: fleece

How sheepskin is being used?