Mamiya RB67 with 127mm F/3.8 Lens

The RB67 Professional was introduced in 1970 with a similar look to conventional medium format SLR cameras like the Hasselblad, but was larger due to the 6×7 cm frame format, closer to the typical 8×10 inch aspect ratio of portraits. However, the RB67 differed visually from other 6x7 cameras of the time, which resembled very large 35 mm cameras.[3]: 168 

There are three successive models: the RB67 Professional (first model released in 1970), RB67 Pro-S (released in 1974) and RB67 Pro-SD (released in 1990). The RB67 is a modular camera system, meaning lenses, viewfinders, ground glasses, film winders and film backs are all interchangeable. It is primarily designed for studio use, but can also be used in the field. There is no shutter in the RB67; the Sekor lenses have built-in mechanical leaf shutters which are cocked and triggered from the body. Focusing is performed with a bellows on the body. It is a completely mechanical camera requiring no batteries.