Rolleiflex's line of 120 SLRs began in 1984 with the 6006. This camera was an evolution of the electronic SLX, and had interchangeable film backs and TTL flash metering. Later models added spot metering, continuous shooting, and even autofocus.
6000 cameras have a host of lenses from Rollei and Schneider-Kreuznach as well as a suite of accessories. Most 6000 series cameras used internal Nickel-Cadmium batteries that no longer hold charge, so alternatives are being produced.