Mauboussin - Jewellery box - unique piece - 18kt gold

Subject: Luxury double deck card set, Mauboussin Paris, in 18-carat gold, mother-of-pearl, and lacquer.
House: Mauboussin Paris (Brand confirmed by signed plaque on the box).
Materials Description
Box: wooden body covered with red lacquer (probably gold-glittered).
• Precious Metal: The clasp, corner nails, and ornaments are made of 18-karat yellow gold (750/1000). The presence of gold is confirmed by the eagle head hallmark visible on the clasp and the master hallmark (see photo).
Main ornament: Rectangular plaque of genuine Mother-of-Pearl, measuring approximately 3.5 cm x 6 cm x 0.2 cm.
Setting: The pearl plaque is adorned with a central heart motif in 18K gold, which appears to be set with small diamonds (or precious stones).
Object dimensions (approximate):
Nacre 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 custom order from Maison Mauboussin, and not a mass-produced jewelry item. I would like to obtain an estimate of its market value (hammer price) from your experts.