This doll is the "October Birthday Treasures" Limited Edition doll, which is actually an extremely popular vintage Barbie clone (often referred to by collectors as a "Barbie clone") manufactured around the year 2000 by Lucky Ind. Co. / Lucky Bell under their Fashion Corner toy line. [1, 2]

While it looks nearly identical to standard Mattel collector dolls, the distinct hexagonal display case and the specific "Fashion Corner" branding on the upper lid set this line apart