R.B. Graflex Jr.

SLR camera made by the Folmer & Schwing Division of Eastman Kokak Company during early to mid 20th century.
RB stands for rotating back. The 2.5 x 3.5 sheet film magazine can be rotated for vertical and horizontal shots.
Dorothea Lange used a large format version of this type of camera to shoot her famous image "Migrant Mother". Many other famous photographers of that time used Graflex cameras.