The deal is expected to close in 2017.
Qatar Luxury Group, the leather goods brand’s majority shareholder, is negotiating with Tolomei Participations for the company’s purchase.
Deal follows Signa’s majority stake in Hood.de last week and six previous digital buys.
Latest online acquisition pumps up Karstadt’s multichannel marketplace strategy.
The offer for outstanding shares will end on June 28, French stock market regulator AMF said.
The investment firm, which targets retail-focused brands in the affordable-luxury segment, wants to develop the label in France and overseas.
The financial holding group plans to invest up to $56 million over the next five years in the company’s growth plan.
Elisabeth Ponsolle des Portes, president and chief executive officer of Comité Colbert, suggested LVMH should bid for the crystal maker.