In 1989, Deere replaced the 6620, 7720, and 8820 with a new line of completely redesigned 'Maximizer' combines that included the 9400, 9500, and 9600 walker combines. These combines featured a center-mounted cab, rear-mounted engine, and more comforts in the cab. Also in 1989, Deere was inducted into the National Inventors Hall of Fame. In 1997, Deere celebrated 50 years of self-propelled combine production, and the 1997 models featured a 50th-anniversary decal. In 1998, the 9410, 9510, and 9610 were introduced. These were essentially the same machines, but with minor upgrades. Deere dealers offered '10 series' upgrades to owners of older 9000 series Maximizer combines. In 1999, Deere introduced the 50 series Maximizer combines. These machines featured significant cosmetic upgrades including a more streamlined appearance, improved ergonomics in the cab, PTO shaft-style header hook-up, and the larger models were available as rotary machines which were a complete departure from the combines that Deere had built in the past.