I'm not sure that this bubble chair is the one that you are looking for: it is an modern armchair in the shape of a bubble. But I thought that you should have the information.

Le fauteuil Bulle par Eero Aarnio en 1968
Basé sur l’idée originale du fauteuil Ballon, le fauteuil Bulle présente le modèle réduit de son design. Comme disait Ludwig Mies van der Rohe : Moins devient plus ! un chef-d’œuvre du modèle réduit.
http://www.eero-aarnio.com/49/Objets/Fauteuil_Bulle.htm

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Note added at 2 hrs (2007-02-12 20:28:32 GMT)
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chaise de dossier à médaillon
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Thanks for the additional information. To me, these look more like dining room or drawing room chairs with a round back. The Wikipedia site lists additional choices of chair backs.

Victorian Rococo Revival Balloon Back Chair
Antiques:Furniture:Chairs
Victorian Rococo Revival Balloon Back chair with open rails and a deeply carved floral crest; in excellent sturdy condition; ca. 1860-80; size: 35" Height of back, 17" Width, 16" Seat height. We have two available.

Dossier à médaillon
de forme arondie créé par Louis Delanois en 1769
http://fr.wikipedia.org/wiki/Dossier_(siège)

chaise "médaillon"
2 Chaises "Médaillon
http://www.achats-malins.fr/maison_jardin/Chaise_4.htm


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Note added at 2 hrs (2007-02-12 20:31:34 GMT)
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I'm sorry my URL for the Victorian Rococo Revival Balloon Back Chairs didn't post. Here it is:
http://www.rubylane.com/shops/piatik/item/PS02-17-05-04

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Note added at 3 hrs (2007-02-12 21:08:12 GMT) Post-grading
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Thank you