Playel Double Grand Piano

Some Facts about Playel Double Grand:

The fact that, little short of a miracle, a double grand manufactured in 1904 - having escaped the catastrophe of two world wars - suddenly appeared for sale in Switzerland in 1995, brought a decisive moment in the career of the Egri & Pertis Duo. The instrument has consequently been in the duo's possession since 1996.

and some info:

The Pleyel Double Grand Piano is truly a unique musical instrument, as only a handful now remain throughout the world. Some 50 double grand pianos were produced in the Pleyel piano factory in Paris but, sadly, most of these were eventually destroyed in the mayhem of two world wars.
This type of musical instrument was originally developed by the company in the 19th century and the last double grand was said to have left the factory in around 1930.

The two keyboards are placed at opposite ends of this 2.5 meter long instrument that weighs nearly 600 kilograms. The brilliance of the design lies in the fact that, although the two pianos are housed in one body, both have their own sets of wires, pedals and mechanism. (With a special switch, the Pleyel design also makes it possible for one of the players to operate the pedals of the other if necessary, and this of course also works the other way round.) At the same time, the casting and the resonance - an important element of the instrument - are common to both. All the sounds produced are emitted in a shared space, the overtones enrich each other, and all of this results in a warm and wonderfully full sound. 

From:
http://www.egri-pertis.com/english/double.htm