Mauboussin - Jewellery box - unique piece - 18kt gold

Subject: Luxury double-deck card set box by Mauboussin Paris, in 18-carat gold, mother-of-pearl, and lacquer.
House: Mauboussin Paris (Brand confirmed by signed plaque on the box).
Description of Materials:
• Box: Wood body covered with red lacquer (probably gold-dusted).
• Precious Metal: The clasp, the corner studs, and the ornaments are in 18-karat yellow gold (750/1000). The presence of gold is confirmed by the eagle head hallmark visible on the clasp and the master’s mark (see photo).
• Main ornament: Rectangular plaque in genuine Mother-of-Pearl, measuring approximately 3.5 cm x 6 cm x 0.2 cm.
• Setting: The mother-of-pearl plaque is adorned with a central 18K gold heart motif, which appears to be set with small diamonds (or precious stones).
Object dimensions (Approximate):
• Mother-of-pearl plaque: 3.5 cm x 6 cm x 0.2 cm.
Context of the Request:
This is a rare piece, probably a limited edition or a special commission from Mauboussin, and not a mass-produced jewelry item. I would like an estimate of its market value (auction value) by your experts.