threepenny vs sixpenny

threepenny and sixpenny both are adjectives.

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

As adjectives, threepenny and sixpenny are synonyms defined as:

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

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