The Black Grand Piano prize from the marketplace event is not exactly the same as the one from that architect house. They have different names and show up separately in inventory. The one from the architect house is called Baby Grand Piano.
They look exactly the same, however.
They don't have the same actions. The one from the marketplace has a shorter action time than the one from the architect house. They both, though, make the same sound.
While the one from the architect house can be placed outside the one from the marketplace event cannot.
