sixpenny vs twopenny-halfpenny

sixpenny and twopenny-halfpenny both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sixpenny	No	Yes	No	No
twopenny-halfpenny	No	Yes	No	No

As adjectives, sixpenny and twopenny-halfpenny are synonyms defined as:

Other synonyms of sixpenny include threepenny, tuppeny, two-a-penny, twopenny.

sixpenny (adjective)	twopenny-halfpenny (adjective)
of trifling worth	of trifling worth