Graflex produced various cameras that became the hallmark for early press cameras although they were also meant for the sophisticated amateur.
The series represented by this camera were true single lens reflex cameras and first appeared about 1900.
They have a focal plane shutter and have full through the lens focusing.
They came in three film sizes as well as in a stereoscopic version.
This version is called RB because it had a rotating back to allow portrait or landscape shots. The shot below shows the back in its two positions. This is seen as one of the great features of the much more modern Mamyia RB67.