sixpenny vs threepenny

sixpenny and threepenny both are adjectives.

Word	Noun	Adjective	Verb	Adverb
sixpenny	No	Yes	No	No
threepenny	No	Yes	No	No

As adjectives, sixpenny and threepenny are synonyms defined as:

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

sixpenny (adjective)	threepenny (adjective)
of trifling worth	of trifling worth
	used of nail size; 1 1/4 in long