The R.B. Graflex Series B is a single-lens reflex roll-film/plate camera made by Graflex in the United States. It uses a focal-plane shutter and a waist-level reflex viewing hood, the format associated with the Graflex SLR line introduced in the early 20th century. The "R.B." designation refers to the revolving back, allowing the photographer to switch between portrait and landscape orientation without rotating the camera.

Auction data for the R.B. Graflex Series B is thin: a single UK saleroom hammer result of £125 in April 2023 is the only confirmed reference point we have, so today's value should be treated as indicative rather than a firm market price. As a wholesale auction figure (excluding buyer's and seller's commission), it suggests complete examples sell for around £100–£150, though condition, bellows integrity, and the presence of an original lens can shift what one sells for in either direction.