The dictionary of photography for the amateur and professional photographer (1897)
Wall, E. J. (Edward John), 1860-1928, Bolas, Thomas · London : Hazell, Watson & Viney · leaf 527
Shutters, Instantaneous (Cl. II., a 2) The Flap and Drop. This is a combination of … the outline. Many shutters of this class are constructed to fit in front of, behind, or between, the lenses. 5*7
Photography
Internet Archive · Getty Research Institute · Public domain (published before 1931). Free to use for anything.
