I bought a Toy Piano Michelsonne in February 2008 in a Paris flea market, it was under a table, away from heavy rain in the odds and ends of the stand ...
Mine is a model rather unusual because it is big enough, I mean, it's a mini upright piano with his three-octave keyboard (!!!!!) folding.
(Edit of 21/01/2011: at the time, I had only seen small toypianos, I did not know existed as great models!)
I disassembled, cleaned piece by piece, hammer hammer, stroke by stroke, oiled, describes, and it is back like new today.
I have no idea the date of manufacture, there is no course code or serial number!
As for sound, well it's the sound Yann Tiersen, the true sound of the Toy Piano, with particular resonances etc ...
I am surprised that no more fans for this amazing keyboard!