hardbacked vs hardback

hardbacked is not a noun while hardback is a noun.

Word	Noun	Adjective	Verb	Adverb
hardbacked	No	Yes	No	No
hardback	Yes	Yes	No	No

As adjectives, hardbacked and hardback are synonyms defined as:

Other synonyms of hardbacked include hardbound, hardcover.

hardbacked (noun)	hardback (noun)
	a book with cardboard or cloth or leather covers

hardbacked (adjective)	hardback (adjective)
having a hard back or cover	having a hard back or cover