Here are some chairs that offer you varying designs. The mold and shape seems to be one and the same, the chairs of which look somewhat simple though providing the necessary functionality that one would expect from the usual chairs out there.
Hans J. Wegner partnered with legendary fabric company Maharam to produce these modified shell chairs which are now officially called the Maharam Shell Chairs.
There are about 20 different pairs available, chairs and fabrics designed to complement each other. Designed in 1963 and only a handful made, the chair actually never really went into production until the 90s when it was reissued and designed with upholstery.