Say a story revolves around a piece of art. The art itself was invented for the story but in order to establish how valuable it is it is attributed to a real person - for instance a newly discovered play by William Shakespeare
. Due to Small Reference Pools
the audience is well aware of who Shakespeare (or whoever) is and is therefore given some idea of why everyone is trying to get their hands on it.
Note that this trope doesn't apply if the work of art really existed
but has been lost
, so to continue with the Shakespeare analogy a story about Loves Labours Won
doesn't count but a totally fictional play would.