call mark vs call number

call mark and call number both are nouns.

Word	Noun	Adjective	Verb	Adverb
call mark	Yes	No	No	No
call number	Yes	No	No	No

As nouns, call mark and call number are synonyms defined as:

call mark and call number: a mark consisting of characters written on a book; used to indicate shelf location

Other synonyms of call mark include pressmark.

call mark (noun)	call number (noun)
a mark consisting of characters written on a book; used to indicate shelf location	a mark consisting of characters written on a book; used to indicate shelf location