German footwear giant Birkenstock is exploring a sale to Luxembourg-based private equity company CVC, The Financial Times reported. : German footwear giant Birkenstock is exploring a sale that could value it at more than 4 billion euros ($4.85 billion) including debt, sources close to the matter told The Financial Times. The company is exploring a sale to Luxembourg-based private equity company CVC, the sources said, but has attracted interest from Permira and at least one other private equity firm.