Around a century ago, there was a fad for dressing up pianos to look as if they were from the Napoleonic period. Because the style of the design is intended to appear much older than it is, it is disguised, so I can't see any features that would tell me how old it really is.
Pianos are hardly ever "rare", special models pop up for exhibitions sometimes, but I can't assess its degree of rarity. Ask an auctioneer or valuer near you to have a look.
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If you find old references or links on this site to pianogen.org, they should refer to pianohistory.info