endorser vs signatory

endorser and signatory both are nouns.

Word	Noun	Adjective	Verb	Adverb
endorser	Yes	No	No	No
signatory	Yes	No	No	No

As nouns, signatory is a hypernym of endorser; that is, signatory is a word with a broader meaning than endorser:

endorser: a person who transfers his ownership interest in something by signing a check or negotiable security
signatory: someone who signs and is bound by a document

Other hypernyms of endorser include signer.

endorser (noun)	signatory (noun)
someone who expresses strong approval	someone who signs and is bound by a document
a person who transfers his ownership interest in something by signing a check or negotiable security