I could tell you where it is, but that would spoil all the fun...
This page contains spoilers! Read on your own peril.
The replica of the Crown and Heart at Carmen's Place
The replicas of the Kurshok Crown and Heart that were crafted for Ma Graham's boys (Eddy and Morgan), but were never used.[1]
They can be purchased at Carmen's Place, both for 750g, after the last city mission, if desired, and will replace the artifacts that Garrett steals from the Wieldstrom Museum in the mission "Still Life with Blackjack".
Bugs[]
In the PC version, they can be placed by activating the pedestals, but in the Xbox version, they do not actually appear in Garrett's inventory, and so have no purpose.