coin bank vs penny bank

coin bank and penny bank both are nouns.

Word	Noun	Adjective	Verb	Adverb
coin bank	Yes	No	No	No
penny bank	Yes	No	No	No

As nouns, penny bank is a hyponym of coin bank; that is, penny bank is a word with a more specific, narrower meaning than coin bank:

coin bank: a container (usually with a slot in the top) for keeping money at home
penny bank: a child's coin bank (often shaped like a pig)

Other hyponyms of coin bank include piggy bank.

coin bank (noun)	penny bank (noun)
a container (usually with a slot in the top) for keeping money at home	a child's coin bank (often shaped like a pig)